I dont mean a version of Windows. They were going to call Windows, Interface Manager.
They actually started off calling it that in 1981 until renaming it to Windows. The first pre-version released two years later was Word for Dos. The extract here can easily be found at wikpedia.org.
Windows 1 and 2 - Early UI
Windows 1.0 GUI
Just after the PC hit the market (August 1981), a project named "Interface Manager" started. It was renamed to "Windows" because the programmers talked very much about the zones called "windows" on the screen.
Rowland Hanson, the head of marketing at Microsoft, convinced the company that the name Windows would be a more appealing name to consumers. The first Windows pre-version was presented in November 1983. It used
Word for DOS-like menus at the bottom of the screen. The 1.0 version (it was numbered 1.01; it is rumored that version 1.00 was actually released but quickly pulled due to a severe flaw), released in November 1985, used pull-down menus like the early
Macintosh System 1.x (Microsoft actually licensed GUI elements from Apple). The shell was a file manager (not a program manager) called "MS-DOS Executive". Applications could be launched from the MS-DOS Executive which minimized itself. The minimizing (called "iconing") was done by transforming the windows into an icon which was placed at the bottom of the screen, in a special minimized windows zone. The maximizing (called "zooming") could extend the window over the minimized windows zone. Windows could not be overlapped, but they were instead "tiled". As a result, two windows could not be "zoomed" at the same time.
Windows 2.0 was an interface-based release. The new window controls were introduced with this release, with the new "minimize" and "maximize" terminology. Windows could be overlapped and the minimized window icons could be moved freely on the desktop.
http://en.wikipedia.org/wiki/Windows_Shell
They certainly didn't want to call it 3000 since that would go over like a lead balloon with the 98-ME crowd. 
