Hi, I was recently just helping my friend build a new computer and here's a problem I've encountered. The system runs completely fine (played tf2 and tft on it for a couple hours), but as the computer geek I am, I tested his system with prime95. It usually starts out fine but if I leave the computer running for a couple hours, it crashes and gives the "send error report" dialogue (consistently having this problem). Here's the confusing part, it runs my games fine and I checked the CoreTemp log and the temperature never went above .

I've eliminated several possible causes to the problem:
1. I'm using the newest version of Prime95 and I used it to test my own system (which had 0 problems running for a week)
2. I used Memtest to check if it was a ram problem, but his computer passed the test with 0 errors.
3. I didn't overclock the system and I left it all on stock settings.
4. I installed Windows XP Pro (SP3), so none of the compatibility problems of Vista-64bit.
5. All the drivers are updated to the most recent available.

The specs of his system are the following:
AMD Phenom 9850 BLACK EDITION 2.5GHz Socket AM2+ 125W Quad-Core Processor Model HD985ZXAGHBOX - Retail
G.SKILL 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory - Retail (Model F2-6400CL5D-4GBPQ)
GIGABYTE GA-MA78GPM-DS2H AM2+/AM2 AMD 780G HDMI Micro ATX AMD Motherboard - Retail (Supports 9850 BE)
OCZ GameXStream OCZ600GXSSLI 600W ATX12V Power Supply - Retail

Any inputs or suggestions would be greatly appreciated.
Thanks
JY

Well, I'm getting the same error even in stock speeds. I mean everything else runs perfectly fine and I haven't really attempted at overclocking (since my friend prefers his system to run at stock).

Most likely your ram voltage.

Most boards come pre set at 1.8 volts, but most quality ram needs 1.9- 2.1 or so to stay stable at their timings.

Set yours to 2.05 in the bios, (safe up to 2.2 on ddr2) and give it a try.

There are a lot of good suggestions already posted.

I recently had some nasty RAM problems with some of the bad batch of Crucial Ballistix in an GA MA78G-DS3H motherboard. The system would occasionally do weird stuff, like shutting down on its own for no apparent reason. It ran Memtest86 successfully overnight, then ran Prime95 for two hours with no errors. I used the computer for other stuff, then restarted Prime95 and it errored-out almost immediately. I went back to Memtest86 and it too reported errors within the first minute. It even froze on Memtest, claiming it received some "unexpected interrupt" or some such.

It's not like the RAM was completely good or completely bad, it just appears flaky, right on the edge of successful operation. (And yes, I made sure it was running at the specified voltage of 2.2V). Since I couldn't trust the RAM, I switched in some Corsair XMS sticks and haven't had any more problems.

Try running Prime95 in the small footprint mode, where it runs mostly in the cache. Do you get errors there? Or do you only get errors when running in the modes where it is using lots of RAM?