Windows Neptune build 5111

Windows Neptune build 5111.1 is a build of Windows Neptune. As of 2024, it is the only leaked build of Windows Neptune. It's also known as "Microsoft Neptune Developer Release" and was sent to developers on 1999-12-27. Much of the branding (including Winver) still says "Windows 2000". Although many files have the version "5.50.5111.1", and this is even the true version in the kernel, the kernel actually reports "5.00.5111.1" to match the subsystem version in its own PE header.

This build cannot upgrade from Windows 98. It includes the Activity Centers, a new login interface and user management application, an early version of Internet Explorer 5.5, as well as the new Help Center and AutoUpdate from Windows ME and several other improvements. It's configured to hibernate rather than shut down by default.

Multiple different copies
There have been several different disc images available online over the years, and most have been modified in various ways, for example to disable the timebomb. The copy currently on BetaArchive was made from the original PWA warez leak from 2000-01-24 and doesn't feature any modifications. It doesn't require a product key, but has an active 444 day timebomb.

NFO contents 

Original disc
In 2011, a person with the nickname iapx432 revealed they have an original disc of a Neptune Developer Release. The contents of the disc were reportedly the same as the leaked copy of 5111.1, and the original volume label of the disc was "NEPTUNE M2". Photos of the disc can be seen in the gallery below.

However, the disk label also says "Software Expires: 6/1/2001". The leaked copy of build 5111.1 has a 444-day timebomb since the date of installation, and an additional date check during setup, which will display a warning but allow the installation to continue. The date which is checked by setup is neither 2001-01-06 nor 2001-06-01, casting doubt on the common belief that the build on this disc is indeed exactly the same as the leaked copy.

Activity Centers
Although this build includes the Activity Centers, they are largely broken or incomplete. Several members of the community have attempted to fix or recreate them over the years, with varying degrees of success.

The three main Activity Centers (Photo Center, Music Center and Game Center) and the Start Page are located primarily in, which needs to be registered to install the Activity Centers. You do this by copying the file from the CD to  and running. Once this is done, the files are located in. The Start Page can then be used as the Active desktop page.

The executables for the above mentioned centers are missing in this build, so the default links to them don't work. It's possible to open the individual centers with  instead.

Login screen
Although the new login screen is functionally identical to the one introduced later in Windows XP, it's actually another HTML application. It's located in, with some of the functionality in. This same login screen was later used in Whistler build 2211, but then scrapped soon after in favour of a DirectUI-based one.

The power button in the bottom left corner will initiate a hibernation by default. To restart the computer, hold down the SHIFT key before clicking the button. To fully shutdown the computer, hold down the CTRL key before clicking the button.

The login screen is listed in the Add/remove programs control panel as "Microsoft Neptune Neptune Logon", but attempting to uninstall it fails.

Windows Identities
This is the new user management control panel applet in, also an HTML application. While the old user management control panel applet from Windows 2000 is still present initially, it will be removed by the login screen code after it's displayed for the first time. This feature is also functionally very similar to its successor in Windows XP.

Neptune defines four account type:


 * Owner - This type of account is intended for people who can make system-wide changes to the computer. A person with an Owner account can make changes to all Windows accounts that have been created for this computer, such as changing account names, pictures, passwords, and account types.
 * Adult - This type of account is intended for people who can make standard changes to the computer, such as installing applications and software.
 * Child - This type of account is intended for children whose activity should be monitored and who should be safeguarded against corrupting computer settings and deleting important system files. Restricted accounts have limited access to internet content and can have limited computer time. A person with a child account can only change his or her own account name and picture.
 * Guest - This type of account is intended for Guests to use the computer. Guest accounts have restricted access to this computer. Settings, Themes and web browsing history will be erased each time a person with a guest account turns off the computer. Only Documents created by a guest person will be saved.

Help and Support / PCHealth
Help and Support (previously called Help Center) has only loose ties to other Activity Centers, as it's actually stored separately from them in  and is built on top of the PCHealth framework. It appears to have been ported directly from a build of Windows ME, because it still contains many references to Windows Millennium. Despite the presence of this new Help Center, the old Windows 2000 Help application can still be accessed from the Start menu's Help option, although a link to it has been commented out in the new Help Center homepage. There is a broken link to the System Restore executable, which is not present in this build; it's unclear whether Neptune was to include this feature eventually or not.

Available support topics are stored in a Microsoft Access database file called  in. The whole program was designed so that the database can be updated, possibly from online sources, using the  program and   MS Cabinet archive.

PCHealth is set to run at every startup to monitor the minidump directory for new minidumps after system and application crashes. If it detects such an event, it will prompt the user to submit relevant information to Microsoft for analysis via the Bug Reporting page in the Help Center.

The Bug Reporting page can be accessed either through Help Center or its dedicated desktop shortcut. It's stored in  before it's installed. Although it's from Windows ME, it was adapted for Neptune. The string at the bottom of the page is "Bug Reporting Page Version 5.00.00.5112", and bug reports are saved to   by default. The Bug Reporting page contains two hidden sections with instructions for submitting additional files, one for DirectX and one for System Restore.

Windows Update Auto Update
Another HTML application shared between Millennium and Neptune. It was meant to facilitate automatic updates via Windows Update, but doesn't seem to be working yet. The initial dialog will only be shown on the first run, allowing the user to read the license agreement and change AutoUpdate settings. Auto Update version in this build is 5.4.284.1, and is located in the  directory. The main executable is, while the HTML UI components are in.

WIA
The new Windows Image Acquisition technology is present in this build. This includes the Still Image Service, new drivers for various scanner and camera models, and a new Control Panel folder for managing them. However, Still Image Service appears to be broken in this build, see the Known issues section for more information.

Fast boot
Fast boot is a new feature presumably designed to speed up system boot time. It's contained in  and installed as a service. It can be enabled in the Power options, but only if Neptune is installed on a FAT partition. On the next boot, Neptune will display a window saying "Optimizing boot". At some point it creates a roughly 2-2.5 MB large file named  in the   folder. The image appears to contain the initial memory snapshot of boot drivers and the kernel. The specifics of how this helps speed up the boot process remain unclear.

The boot screen is displayed with a lime progress bar instead of the usual blue if Neptune boots in fast boot mode.

Internal strings call this "Profile Assisted Boot Accelerator" or "PABA". , the Disk Performance Driver, has also been extended to support this feature.

Prefetcher
This build is the first to have the Prefetcher feature which was later introduced by Windows XP. It's meant to speed up system boot and application loading time by caching the required files. .PF files are stored in the  folder. Prefetcher is enabled by default; to disable it, create a new DWORD value named  in   and set it to 1, then restart the system.

Application Manager
Application Manager was envisioned as a new component for centralized management of games and other applications, providing functionality such as disk quotas and file clean-up. This is provided by  and , but the user interface for this feature, which was added to   in Windows ME, is not present in this build yet.

This feature appears to have also facilitated Game Activity Center's game discovery feature at some point, before the Game Center was dropped. Later it became part of DirectX 8.0, as it is present in the early beta build, but was subsequently removed before the final release.

Resource Manager
This appears to be a new driver-related component, but its purpose is not yet understood. It's comprised of two files, a "WDM Resource Manager" driver, and the "Resource Manager User Mode". It was later added to Windows XP build 2202 as well, but was then removed again soon after.

Net crawler
Net crawler was introduced in Windows ME and then ported to Neptune. It automatically searches the local network for shared folders and printers, and then creates shortcuts for them in the My Network Places folder. This feature is enabled by default in this build, but can be disabled by checking the "Disable auto browse for shared folders and printers" checkbox in the advanced folder view options.

Firewall
There is a checkbox to "Enable Firewall mode for this connection" on every network connection's Sharing options page, which suggests a firewall feature of some sort may have been planned for Neptune. It doesn't appear to be functional, though. A built-in firewall was later included with Windows XP.

Submit a comment
Also a first appearance in this build is the "Comments?" link in the title bar of most dialog windows. Clicking it brings up a feedback dialog from  with a brief form to explain the problem. This would then be sent anonymously, along with a screenshot of the offending window, to Microsoft.

The "Comments?" link in dialog title bars can be disabled by changing the DWORD registry value  in   from 1 to 0. This feature was also added to Windows XP build 2202, but the relevant registry key has changed and also allows for changing the link text itself as well.

One-touch setup
One-touch setup is used to launch an automatic unattended upgrade, possibly intended to be launched from a network share with the build files.

Upon launching, it copies  to temporary files and displays a user account name prompt. It then attempts to modify the file with the specified name and the current computer name. This is affected by Windows marking files copied from a CD-ROM as read-only, making the application silently fail unless one removes said attribute from the copied file when the initial window appears. Finally, it launches the regular setup executable in unattended mode.

The executable has a file version of 5.00.1636.1, the same as the setup billboard library in Windows XP build 2250. It is unknown whether this is coincidental or the two features are related in some way.

Timestamps in the unattend file suggest that the feature was implemented around 1999-08-09:
 * / Revision History:
 * /     990809  dane    Created.
 * /     991104  nickl   Modified to facilitate an unattended clean install.

Neptune Upgrade Service
and  setup libraries also contain two extra dialogs, one of which has a placeholder string saying "Files for Neptune build 5XXX are now available.". This dialog actually stays hidden, but is needed to run the second dialog with the postpone options, which is then displayed to the user. also contains a commented line which would add  (this program is missing from the leaked copy) to the list of programs to be started on system startup; the program is labeled as "Neptune Self-Host Reporting Daemon".

It is believed these were all part of Neptune's new self-hosting update system. NTCSelfh would probably regularly check for new builds in the background and run  with the   and   parameters on a network share. Setup would then copy temporary files to the machine and display the mentioned dialogs to inform the user a new update is available, with the build number obtained from the copied.

This dialog can also be manually triggered by running. Clicking Upgrade Now will begin the installation.

Neptune Credential Manager
appears to be the precursor to the Credentials Manager from later versions of Windows, meant for managing various user credentials in one place. It's described as an "internal Microsoft tool" in the UI, while the file description says "Neptune-to-Neptune Upgrade".

Trying to add a credential on a non-owner account will result in an error message saying you can only add credentials on accounts with administrator rights in this build.

.NET Framework
The file FUSEWIN.dll references various nonexistent files, one being mscoree.dll. In the context of the .NET project, Fusion was the codename for the CLR Loader, a component that loads CLR assemblies into .NET AppDomains. In the .NET Framework 1.0 Beta 1 (the earliest version available as of 2020) mscoree.dll is present and is a component of the Common Language Runtime. In addition, functions within FUSELOAD.dll reference .NET components such as ASSEMBLYINFO and assembly creation. This file, while nonfunctional due to missing imports, is a component of an extremely early version of the .NET Framework, several months before its PDC tech preview (from July 2000) and potentially even before the .NET name.

Another component of the .NET framework found in Neptune is SYSXML.DLL. This is a .NET assembly using what appears to be an earlier header format and cannot be opened in .NET decompilation tools, although the Cor20 header does show in dnSpy. It is the System.Xml.dll component used in .NET apps for interfacing with XML files and refers to itself as such internally, although it refers to itself as "Microsoft(R) XML+", with the file description being "XML+ (MSXML for COM+)".

Joindom
is set to run at first login and is used to create the first user account. It's described as a "pre-release Microsoft utility" in the UI, several strings inside this file suggest it's part of the out-of-the-box experience (OOBE), while the file description says "Neptune-to-Neptune Upgrade".

My Pictures Slideshow screensaver
This new screensaver first appeared in Windows ME build 2394, and was ported to Neptune sometime after that. It plays a slideshow of the pictures in the My Pictures folder as the screensaver.

Neptune Server
This build includes the "Configure my server" wizard from Windows 2000 Server editions, which is rather unusual for home and professional editions. An interesting fact about this particular component is that it's also an HTML application.

There are also several "Neptune Server" strings inside several setup files, though this could simply be the result of a mass rebranding effort. Although multiple SKUs are defined in the anti-trust documents, it's not entirely clear whether Neptune would also include a server edition.

Driver signer
Drivers in this build are signed by "Microsoft Consumer Windows Publisher", which was also used in Windows ME, but not Windows 2000.

Multiple desktops
The MULTIDSK.EXE file in i386 enables the creation of multiple desktops. This was introduced in the Option Pack for Windows NT 4.0 but is new to the base OS in Neptune.

VirtualBox IDE bug
Like many late builds of Windows 2000, this build also suffers from the IDE bug in VirtualBox during installation and requires the workaround to be applied before installation to prevent it. In your VirtualBox installation directory, open a CMD window and run the following command:, where you substitute VM name with the name of your virtual machine. After the installation completes, you can run the same command with a 0 at the end instead of 1 to disable the workaround as it's not longer needed.

Alternatively, you can also try clicking your mouse and pressing keys on the keyboard very fast, to force a slowdown that will prevent a reboot.

Still Image Service
The Still Image Service is broken in this build and will fail to start. Because it's set to start automatically by default, it causes a delay when Windows Explorer is loading. This can be prevented by setting the startup type to either "Manual" or "Disabled" to prevent the service from starting automatically.

Attempting to open the new "Scanners and Cameras" Control Panel folder will fail for the same reason, hanging the Explorer window in the process.

Updating Internet Explorer
Updating Internet Explorer on this build is not recommended, as it tends to break the HTML applications, especially the new login screen, which renders the build unusable.

Hibernation and shutdown
As mentioned at the start, this build is configured to hibernate by default. If ACPI is not supported or properly implemented on the (virtual) machine, the system state will still be saved, but a non-ACPI shutdown dialog will be displayed, telling you it's now safe to turn off your computer.

Shutting down can in some cases also result in a restart instead.