CS4 Sloooooow Laaaaaaag

[Johnboy2978]

So I just downloaded the trial of cs4 extended. I have been using cs2 which works fine w/o any problems. On cs4, I notice a very distinct lag and also a weird thing w/ the crop tool in which it won't allow me to click in the dimensions window and type in the dimensions I want to crop. Instead, if I go to the left of the window, I can drag like there's an invisible slider there. Really strange. So any guesses why I am having these problems? I think my pc should still be up to the task and am not really willing to invest more money in my pc right now.

Specs:
Running Win XP Pro SP2
Pentium 3.0GB core 2 duo processor
4 gb DDR ram
nVidia GeForce 7100/nForce 630i 512mb(which may be the culprit)