vista and older games(painkiller)

i have a amd 64 athlon xp 5000+ duel core,using vista,any tips on semi older games like painkiller and vista.i play with win xp and its fine,but vista i cant get the speed down,i use a 8500 gt nvidia card and 4 gigs memory,so im guessing its vista,graphics are perfect just the game is major unstable,tried every viewable setting and network settings also and it wont work right.any suggestions..lol besides never playing it on vista..lol.thanks.

i didnt try the game on vista itself.ive played other games like halo and it works great,but i should have said painkiller online gaming...but thanks.ive heard others talk about the same problem and there is a fix called runfirst,amd said its a hyperthreading problem so who knows lol,i downloaded it and it works great now so ill just see how it goes,again thanks for the help....oh amd also has a optimiser driver for that also for users running duel windows xp.maybe painkiller on 64 bit vista is the tricki would think it should be being a duel core 64 bit and vista 64 bit,sounds logical.[/b]