Check out http://www.ntcompatible.com/0.shtml
You can find the compatibility of most games under WinNT
(same as Win2k). You can also find ways to make it work
even if the game is Win95/98 only.
Quake3 is definitely working under Win2k. I also have AOK
and Jane's F/A-18 working on my Win2k box. Good luck.
BTW, I checked the above site, Hero3 appears to be working
under Win2k.