WinG
 

On our Programs page

Additional reading:
Wikipedia page about WinG
Copy of Microsoft's support page for WinG (courtesy of web.archive.org, original page no longer online)
WinG 1.0 Bug List
A discussion on the former LTF forum (courtesy of web.archive.org + Google Translate, original page no longer online)

Can be downloaded from:
* Microsoft
* Microsoft, alternate server
* And, of course, Abandonia