If you use Media center at all as a DVR make sure it isnt running when your gaming. While XP MCE used to give me an Icon on the taskbar telling me it was recording Vista seems to record silently and often.
Heres my example. Even though I had MCE to record Stargate only during its first run and no repeats it would record the first run and all the repeats because the channel wasnt sending all the info as to when it originally aired etc. it got to the point i opened MCE to see the show and i had about 27 episodes after a marathin from a season that aired years ago.
I have also noticed most popular antivirus programs were running at prime gaming times and really slowed me until i changed the schedules.
Just a couple of other things to check while looking into punkbuster.
