BSOD nv4_disp.dll

I have just started a new job and my pc keeps crapping out, all of a sudden, it will just stop working... cannot get to task manager or anywhere. It just stops at random times. I am using a dell dimension 8300 running xp with what I believe is an aftermarket Nvidia card but not sure. A couple of times b4 when I got a BSOD it had a message for nv4_disp.dll. I have been reading up on this problem and it seems pretty common. Well I have tried most of what I have read about as far as fixes. I have tried updating drivers, I have disabled and went back to the basic windows video controller, all to none avail. I hate to reformat bcuz I have work that needs to be done yesterday!! I'm wondering if anyone else has had this problem and successfully solved it? Please help!

Also, I have upgraded the RAM to 2GB recently. I was having the problem b4, just not nearly as often. Could this have something to do with it? I took out all of the old RAM and replaced it with new so the brand would all be the same. Should I have left one stick?? Would that have anything to do with this issue??

Thanks,

Frustrated xp user!