Video Card Problem

I've just had my Computer repair guy put this on my computer, and straight away I started getting problems. He cured the initial ones but now I've got this "Blue Screen of Death" comes up now and again crashing the computer with a message saying I have a problem with nv4_disp (which upon searching, doesn't appear to be in the computer anyway!). I've tried re - installing but the installation CD has various installation possibilities, and to be honest I don't know which is the correct one, and had to take his word for it (my Comp. guy). Does anyone know how to get rid of this crash problem? I believe the nv prefix stands for NVidia.

Any help appreciated

Steve

Model No.

Asus Series V9400 X/TD/64M/A