I am having the same issue, but i am using windows 7 64bit home edition. All my drivers are updated to the newest versions out there from the manufacturers as i thought that might be the case, but it is not. It happens especially when i have 2 - 3 windows open while i transfer files from one drive to another, or when i play a game, no matter what type of game. I thought it could be an overheating issue, but everything is running between 47c - 53c. I even painstakingly uninstalled each component to check the problem out, but that did not work either. I think there must be an incompatibility issue with W7 with older boards and peripherals even though everything is updated. Maybe another new MoBo and memory and GPU is required, or just go the whole nine yards and get a new PC. To answer your question though, when the screen freezes, does he have to do a hard reboot, this is what i have to do, there is no blue screen error as the desktop just freezes. If it's a hard reboot, then most likely it could be a bios problem, as i think more likely with mine as that is the only thing i have not updated yet.
I have been battling a similar problem with my sons Compaq Presario Cq56 for the past two months.
It started out as an over heating problem caused by the fan exhaust vent being clogged.
Cleaning the fan vent requires a complete dissemble and mother board removal (stupid laptop engineers).
Once the vent was clean, the system was much better, but would still freeze in a few minutes if I tried to run any program that use opengl like angry birds or Virtual DJ Pro.
So another complete dissemble (total dissembles is at 7 so far) to replace the GPU pad which I had to wait 8 days for it to arrive from china (.99 and free shipping, perfect size). So now instead of the system freezing 2-3 minutes after I start an opengl program, I might get 10 minutes.
I updated all the drivers for the system from the HP web site.
I ran sfc /scannow. it did not find anything .
I have been running GPU-Z, Speedfan, and Core Temp to get an Idea of what the system is doing.
One thing I noticed is that the GPU-Z was reporting that the GPU clock was around 675mhz.
Thats about 250 mhz faster than my other laptop that does not have any problems.
My other laptop has an ATI mobility Radeon X1400 GPU with dedicated 64mb of GDDr3 memory according to GPU-Z.
As a last ditch effort to try and get resolution to this issue, I removed my pc5300 (667mhz) memory from working laptop (fujitsu lifebook 3530) and put it in the ailing Compaq, which requires pc6400 (800mhz) memory.
This solved the issue. I will write it off as bad memory caused by the over heating issue. My son let the over heating issue go a long time before he got me involved. Only when he could not use his computer at all did he get me involved.
Bottom line is that his 2gb ddr2 pc6400 800mhz ram works fine in my Fujitsu laptop which supposedly does not support 2gb ddr2 or anything above pc5300 667mhz ram.
GPU-Z reports the GPU clock on his system with the pc5300 memory as 475mhz and the system no longer has any issues.
I upgraded his processor from a single core Celeron to a dual core Pentium of the same speed (2.4ghz) and still, the system does not have any issues.
I will not buy replacement pc6400 memory for his system because his memory works in my system. Which makes me believe that the GPU has been compromised to the point where it can not handle the faster memory.
I could be wrong, his memory could be faulty and works in my system because of the slower bus speed.
Ether way both computers are working fine now. I hope this helps someone.