2-yr PC randomly crash after installing xp64?

Hi,

I had been using a my Dell XPS 410 for about 2 years. (Core 2 Duo E6400, 4GB RAM, Nvidia 7900GS) There was a 32-bit XP installed on C drive and later a 64-bit XP installed on G drive. The dual boot had been running smoothly for half year.
About 3 weeks ago, I see no usage of the 32-bit, so I reformatted the C drive and
installed 64-bit XP from scratch and the whole system became really unstable since then.
It will flash a blue screen (so fast that I couldn't read or take a picture) and reboot
itself. This happens randomly, sometimes after working for maybe 30 minutes, 2 hours, 5
hours, sometimes after 8 hours working. But usually the crash happens within an hour of
use. I just can't predict when it's going to crash or find a pattern of causing the
crash.

I have tried:
1. lower the power consumption (take off all external HD and accessories)
2. swapping RAM (I added 2 gig RAM to 4 gig in total after the first year)
3. duster the machine and motherboard
4. redo the x64 installation with brand new HD from scratch
5. update BIOS to the latest from Dell
6. use BurnInTest to test and shown "no error" in all components I asked to test.

But none of them can stop the random crash. The only thing I can think of that I haven't
tried is putting on a new motherboard. Could anyone tell me what else I can do to fix
this? It's been 3 weeks, and I really can't keep working with this random crash machine.

Truly appreciated,
Jason

Thank you. I am not familiar with replacing or fixing the motherboard caps, but I will google it and see if I can find a clue.

Also, have you tried get a new motherboard? I check the MB price for my machine and it is around 80 bucks. If the problem is from the motherboard caps and I can't fix it, will replacing the MB fix the random crash?

Thanks.