Windows 95 build 73f

Windows 95 build 73f is a Milestone 5 build of Windows 95, leaked on BetaArchive by member sunnyblueman in 2014.

It is nearly identical to the previously leaked build 73g. The main difference is that this is an internal build and thus includes an internal version of the WinBug utility, while build 73g was released to external testers and thus features a different WinBug. It is safe to assume earlier compiles of this build (73a through 73e) also exist.

CAB32 loading error
This build has a problem loading  after setup. To allow the shell to load, edit  in the root of the system partition by changing the lines   and   to   and   respectively. You can do this by using a DOS or Windows 9x bootdisk with a text editor on it, or by mounting the virtual hard disk image in Windows and editing the file there.

Beta Site ID and Password
This build is the earliest known build to require a Beta Site ID and Password to install. An exhibit from Comes vs. Microsoft mentions that this feature was added in response to the original warez scene leak of build 58s. The protection works by having the last four digits of the password be derived from an MD4 hash of the beta site ID, the first four digits of the password, and a string in SUWIN.EXE resources. The fifth digit of the password is a check digit; if this is valid, the setup appears to continue but if the password used is for another build, setup will error before copying files with the "General error 57", a red herring that fooled the warez scene at the time, OSBetaArchive members a decade later, and BetaArchive members a few years after that.

There is a backdoor in SUWIN.EXE; an encrypted resource contains a list of network shares. If one of these shares exist, the user is not required to enter a Beta Site ID or Password. This feature was added for internal Microsoft testers, and when found by reverse engineers, made the protection easier to crack.

This protection was removed around build 311, but was reused for early Internet Explorer 4.0 builds (post-Nashville Plus Pack, pre-Platform Preview) and early Windows 98 builds (removed sometime before build 1351, but its SUWIN.EXE changed the network share list and password derivation string).