i would go with windows 7. i like xp but xp wont recognize over 2GB of RAM
--------------------------------------------------------------------------- Give a man a gun, and he can rob a bank. Give a man a bank, and he can rob the world. Give a moose a cookie, and it will probably want a glass of milk. -Wisdom
I'm throwing in another vote for Win 7. It's probably my favourite version of Windows. Compatibility is great. I've never encountered any problems installing old games, or new ones for that matter. At least non due to the OS version.
Well, that's a lie, I have had problems with old games, but that's only because I'm running the x64 version and old EXE's don't like that (unfortunately, not even compatibility mode fixes this problem).
So yeah, Win 7 definitely. It actually uses less RAM "out of the box"* than previous iterations of Windows (XP and Vista). Having said that though, more RAM is always better even if you don't need it. >4GB though and you'll need the 64 bit version.
*By out of the box, I mean a completely fresh install before you've started putting anything on it.
(Sorry, only just noticed I'm a few days late on this one <.<)
[Edited by Skyheart, 12/26/2010 1:12:06 PM]
--------------------------------------------------------------------------- "Remember the good old days when you could just slap Omni-Gel on everything?" - Shepard, ME2
"Not right now. Trying to determine how Scale Itch got aboard. Sexually transmitted disease carried only by Varren..... Implications unpleasant." - Mordin, ME2