2015-05-04 APN Content on this page, much of which was duplicated, has been merged into the above pages.
Major versions of Windows include:
Tcl 8.6 requires Windows XP or later. Use 8.4/8.5 for earlier releases.
Microsoft is no longer the only provider of the platforms implementing the Windows API: just by far the most dominant. There's also Wine (providing support for Windows apps on platforms like Linux, FreeBSD and BeOS) and ReactOS (providing an alternative Windows compatible operating system).
peterc 2008-06-13: getWindowsAPIVendor is a small but handy proc for detecting which win32 code base your app is really running on: Wine, ReactOS or Microsoft Windows. This can be used for tuning your app or informing the user of support/non-support.