I'd suggest you have your hard drive checked, then. Sounds like the problem is a little deeper than the game program.

I had some problems playing Baldurs Gate which sound similar to what you have described. I used msconfig to close all other applications and disconnected from the internet. Part at least of the problems I experienced were due to the intrusion of "update" messages from my McAfee Virus scan and from other internet messages arriving while I was playing. Hope this helps.
Dandad.

thank you all it helped ;)