Ati Mobility 9700 problem

Hi there!Very odd problem with my laptop. It's an asus a4000k series with ati mobility 9700 (64 mb). Everything has worked great since two days ago. Since then, every time I play a video file(every kind divx, dvd, mpeg) with every player i get the first frame of the video and I can hear the audio track. When I close the player the system crashes. The only way I can see a video is reducing the acceleration slide in the "problem solving" tab of the video properties. I use official and last asus providen drivers. I tried to reinstall the system but no luck. I tried to install omega mod drivers but nothing changed.
Can you help me????Thank you
p.s I have windows xp home sp2