9800gx2

but b4 u add the ram, u must check ur motherboard sin.

does ur old motherboard support ram more than 512mb??

cos old m/b only can support up to 512mb.

and try to do the "disk defragmenter".

the best way is reinstall the window os if it is allow. it can kill all virus and delete all unused rubbish exspecially when u uninstaling the old software.