3D apps are "jerky" snd "skipping" *not the vdeo card*

[Drexx]

A few days ago all the 3D apps on my pc (games,screensavers ect..) started "jerking" and "skipping" at first i thought it was my video card but i put a new card in and it still did the same thing. I have all the current drivers and directx 9 installed. Anyone have any ideas on what this could be? its very annoying. *also on a side note, i doubt this means anything but i'll post it in case it helps. The problem started RIGHT after running disk cleanup and deleteing my windows/temp plus i uninstalled Maya right before this. Thanks guys..ANY help would be greatly appreciated.

[Drexx]

Also, when i reboot my pc everything is fine and runs perfect for about 15-20 minutes, then it starts messing up again. Like I said it sounds like the what happens when a video card is overheating, but this cant be it since i put in a different card and the same thing still happens.

[redwench]

get and run sandra, see if it flags anything. a ram and/or cpu monitoring program would be good too.

[Ocean]

hard drive being accessed by rogue software, or heavy defragmentation perhaps.