graphical problems after reinstalling XP Professional

Hello,
On the computer, which is connected to the internet, I have started regularly doing a clean format of the HD and reinstalling XP.
The first time I reinstalled, I had to due to a corrupt OS. And I had a very bad transition onto the welcome screen (stripes turning a darker blue instead of a screen fading to blue).
As this reinstall was corrupt again very soon due to a broken hd, I had to install again onto a new hd. I was hoping this problem would be gone then. But it wasn't.
And now, another reinstall later, this problem is gone. But I have a different graphical problem. A considerably more annoying one:
Whenever I move a window, or scroll down/up in a program, the computer almost comes to a standstill, and everything scrolls down/up/the window moves in stripes or steps..taking about 5 seconds or more each time..and during that time, the mouse will move just as slowly. although the computer responds relatively quickly to keyboard commands (eg: closing a window)
Between the second and third reinstall, I installed a seperate graphic card so that i could connect two monitors.
Now I'm wondering what on earth could be causing this problem, and if there is a way to solve it?
I don't particularly wish to be stuck with it until I reinstall again, and I get another random problem
El

Hello,

One possibility is that device drivers needed for smooth operation of the keyboard and correct rendering of graphics have not yet been installed on the computer.

Try visiting the Windows Update web site after reinstalling Microsoft Windows XP and letting it install just the device drivers for your computer's hardware.

Does that make any difference?

Regards,

Aryeh Goretsky