new pc help plz.

[kenster9119]

ive just upgraded from a 2gig athlon xp to a 3 gig xp 64 bit edition cpu,board is a asus k8n,512 kingston mem,256 ati 9600 radeon,with the old system space empires ran fine,now with the new one its really slow as in my ships take longer to move and when i click to build things i have to click a few more times for it to register and add things to the queue,but the new halflife 2 and need for speed underground 2 just fine at nearly max settings,and ideas would be great,ta.