There are still some usefull things in there...
For example, source code to (or partial source code to): (either NT4, 2000 or both)
user32.dll
win32k.sys
gdi32.dll
kernel32.dll
ntoskrnl.exe
ntdll.dll
Plus source code to several MS utillities like link.exe
Plus, you get source code to a fair bit of upper-level stuff (IE bits and such)
Not to mention that you get the source code to the famous Solitare game
