Microsoft Online Crash Analysis - FREE

http://oca.microsoft.com/en/windiag.asp

Remember memtest86 or memtest (great products)
How about a free version that you can trust with mission critical hardware and software from Microsoft for FREE.

Windows Memory Diagnostic

This boots from a CD and will test you RAM and the memory subsystem on your motherboard for errors. I recommend running this app anytime you build a new machine. Often times you don't use enough of your ram to test all of the address space. When you do run into a problem you won't know whats causing it. I usually swap out hardware such as memory and the processor to determine if those are the cause. Not everyone has that option and in the case of a bad motherboard this wont help much. The first pass usually takes 30 minutes. What do you have to loose. Burn this disk today so you have a copy when you need it. You never know, Microsoft may not offer this up for ever.