Maybe A Graphics Card Issue..HELP!!

Hello all I'm new here and need some help with my pc. I've built a machine with these specs:
Athlon XP 2600+Barton OC'd to 3200+
Asus A7n8x deluxe mainboard
1 GB Corsair TwinX 3200
160GB Maxtor SATA HD
NVidia Quadro 4 900 xgl
The problem I am having is when I'm playing graphic intensive games about every 25 seconds or so the game will pause for .01 sec or so. I mean it is more of an annoyance for me than anything this really doesn't make the game unplayable by any stretch. But can you imagine after building a machine and having a glitch like this? I've tried shutting down all running programs, shutting down my internet connection, I've been scanning for adware and viruses every day for about two weeks now, i've shut off disk indexing, i've also played with the agp aperture (sp?)size in the bios, setting my clock timings back to what they should be and nothing seems to respond to it. I've also went as far as in the games to actually shut all detail off and all graphics settings to the lowest settings and even in games that used to play fine on my old 800 mhz dell have this glitch that is driving me crazy.

If it is of any help it seems as if the hard drive may be the culprit, but I've had bad luck in the past trying to go through XP's list of running services to shut off any services I need without disabling the ones I do need.

Anyone aware of any scanning utilities that may help me with this? Will Norton Utilities work? I have also had bad luck with this utility and just assume do it all manually if possible...

Dan