When I play Call of Duty2 or Counter Strike Source my computer starts studering like its getting lag spikes, but there isnt a problem with my internet.It seems to studer less when i turn down the graphics. It all started when my computer crashed and I had to reformat my hard drive. and thats when it all started. I have a 6800 nvidia graphics card 1.7 ghz./ 1 gb RAM and windows xp os.

Your 1.7 ghz is the bottleneck in your system. Although you have a 6800, but having a 1.7Ghz will not max out the true potential of 6800. Games like COD2 and Counter Strike Source are not CPU limited games than GPU w/o FSAA or AA...

Solution: Upgrade your CPU to 3Ghz+...

TMP-Man

Asus P5P800-SE
P4 506 @ 4200Mhz 1.45v
Thermaltake CLP0024 w/ 1700RPM 92MM + AS5
1GB Corsair 2-3-3-5 DDR400
120GB/300GB 7200RPM HD
Radoen 9500 mod 9700 @ 375/600 CHS+RHS

you did not give us your full specs, telling us you have a 1.7Ghz CPU is not telling us much. What board do you have? What edition of 6800 do you got, 128Mb NU? Have you updated your motherboard's chipset? do you have the latest DX9.0c version (june)?

Upgrading is not always the best solution, you can make an $800 rig run faster then an $1800+ rig provided the right knowlegde (i.e. tweaking, overclocking), but TMP is right if you have an 1.7Ghz willamette P4, you might aswell.

updates should be installed in this order:
1)mobo
2)window's service packs/patches
3)DirectX
4)video Card
4)Sound Card
6)bios