I've got a rather older setup, but i keep it running smoothly. Not too into the newer games, so it doesn't cause me much trouble. I also don't plan on "upgrading" to Vista until most of the quirks have been worked out (and obviously i have a new computer), so no problems there.
Dell (

) Insprion 5100
Windows XP Pro / Mandriva 2007.1 (dual boot)
Pentium 4 @ 2.66ghz
533mhz FSB
768mb RAM @ PC2100
120gb HDD & 250gb external