Stuttering game cinematics, screensavers and even scrolling

Microsoft Windows

I am experiencing stuttering in gameplay, screensavers pause and when I
scroll pages I get the same pausing. It pauses consistently every 2 seconds
for not quite a second. Very annoying in a driving game. The sound is always
fine. I have updated video drivers, direct x, bios and keep my comp updated
through auto update. I reformatted a few times, 1 time actually clearing it
up, then I installed Dungeon Siege 2 and the stuttering came back. Since then
all reformats have failed to clear it up. I even used different versions of
Direct x thinking it might be a conflict with no luck. Running:

AMD Athlon 64 3000 on
Abit AV8 Via K8t800 Mobo
512 mb pc3200 ddr 400mhz
Maxtor 80gb SATA hd
BFG geforce 6600gt AGP

I have been searching forum after forum with only a couple references to
this prob, but no fixes. Thnx for your time
Did you downnload the newest CPU driver from AMD site? Also I noticed in the
pass when I had AGP is that I had to find a sweet spot in the BIOS for the
AGP memory. Try lowest then work your way up till it starts acting up.
Yep, forgot to mention that as well. Updated that driver too. I did look int
the BIOS to check memory but I didn't see anywhere to change it. The only
place I saw it was fixed with no way to change