Windows 1.0 Premiere Edition

Windows Premiere Edition is a pre-release version of Microsoft Windows 1.0. It was originally sent to key players in the computer industry by Microsoft to prove that their product wasn't vaporware (it had been delayed several times before). Before releasing the official version, 1.01, the memory management code had to be completely rewritten; this would be the key difference between Premiere and 1.01. It was compiled on 1985-07-30.

A build was leaked in 2008, purporting to be the Premiere Edition. It's dated 1985-08-17 and still remains widely available online, even though it's just 1.01 with version string changes. In 2014-03, BetaArchive user trueyanksfan claimed to have the real floppies, and also posted a photo of them. It was later discovered that his disks were partially overwritten. On 2014-12-18, a set of disk images from the real Premiere Edition was released by the BetaArchive user Alias.

Image from Microsoft's FTP
An image of an IBM PC 5170 (IBM AT) running this build exists on Microsoft's public FTP server, however, there are doubts about its legitimacy. It's believed that the image is too clear, bright, and flat to be a genuine photograph of that specific monitor.

Tandy Trower's Article
In The Secret Origin of Windows, Tandy Trower, the project manager for Windows, described the Premiere Edition:

"But by the early summer of 1985, we were still not close to being done, so Steve [Ballmer] declared we should release a preliminary release that I dubbed the Premiere Edition, which we provided to key application vendors, analysts, and members of the press for feedback and in partial fulfillment of Ballmer’s promise to ship the product that summer."

- Tandy Trower

At the time, Windows's release had been postponed several times, leading some people to conclude it had become vaporware (software whose release is promised but never actually followed through). This lead Microsoft to make the decision of releasing a preliminary version before it was completed, which they dubbed the Premiere Edition.

In the same article, Trower also mentions that:

"Then just at the point I was starting to feel more optimistic about wrapping things up the architect of the memory management code told me he found a critical defect in its design and would need to re-write it, basically rendering all testing to date useless."

- Tandy Trower

Additionally, he discusses the release of the rewritten Windows 1.0:

"By November, we had finished testing and come up with a solid release. [...] That release, being after the earlier “Premiere” release, was known as version 1.01."

- Tandy Trower

That implies that there was no final release designated as 1.00, making 1.01 the first truly public release (Premiere Edition was a limited preview).

Fake build
A build of the Premiere Edition was leaked in 2008 and was available on BetaArchive for years before it was removed, but can still be found on many other websites. That build has since been confirmed fake for the following reasons:
 * Microsoft's developers stated that the entire memory management system had been rewritten between Premiere Edition and Windows 1.01, yet the leaked build's kernel is byte-wise identical to that of 1.01. Even the smallest code change would show signs that this version was different, but nothing had changed between the leaked version and 1.01 despite that.
 * The version provided to BetaArchive had included WRITE.DAT (a file meant for Windows Write), which was not originally part of the Premiere Edition. The leaker stated that it was a "mistake" and that Write was there only as an experiment. It was later removed in a re-upload, but the original tampering brought the build's legitimacy into question.
 * The leak originated from betaguy224, who had a questionable past of providing fake material.

Another difference between the fake and real Premiere Edition are the system colors. The fake build features the same color scheme as 1.01, while the real PE has a black and white color scheme by default (some applications are in color, though).

Trueyanksfan's floppies
On 2014-03-16, a BetaArchive user named trueyanksfan claimed to have the original floppy disks. Later on, he also posted a photograph depicting four 5¼" installation disks with "Premiere Edition" clearly written on them.

A few months later, on 2014-09-12, he posted an update, revealing disks 1-3 were overwritten and only disk 4 survived. He also posted a screenshot, claiming that the dates of the files are near the end of 1985-10. It has since been established that the files on his disks are from a later build. The surviving files are mostly applications, such as Notepad, which already have the version number 1.01.

Alias' floppies
On 2014-11-29, BetaArchive member Alias, who was an intern at Microsoft in 1985, posted a picture of the full disk set and the build running on his IBM PC XT. Alias has since shared the genuine version of Windows Premiere Edition with the community. It was made available on BetaArchive to everyone without the need for FTP access.

http://www.betaarchive.com/forum/viewtopic.php?f=59&t=33024

InfoWorld article
In Issue 26, Volume 7 of InfoWorld magazine (dated 1985-07-01), an article called "Microsoft Ships Windows" was published. The article's contents agreed with Tandy Trower's statements, ranging from the release date to certain details (such as the software being given out to "software developers" and "independent software vendors"). It does not, however, mention the name "Premiere Edition" anywhere, and it's entirely possible that the screenshot presented is unrelated to the Premiere Edition, and instead came from an older build between the beta and PE.

Other sources
Stephen Manes and Paul Andrews (1993), Gates, New York: Doubleday, ISBN 0385420757 (a snip talking about premiere)