different blue screens of death, don't know whats wrong

Hey guys,
A couple of weeks ago my computer started crashing with the BSDs, and they've been getting more frequent. The error codes range from 0x000000F4, 0x0000007A, d0000144 and maybe a few others that I don't remember. When I got the first message I was installing some graphics app from stumbleupon (can't find it again). I didn't make any hardware changes to the machine at all.
Right before the BSD the machine usually slows down like its thinking a lot...

I reformatted the drive and reinstalled windows, (got a BSD a couple of times during the install, but the last time windows installed without one).
I ran memcheck and WD diagnostics on the hard drive, both without any errors.
At this point I'm thinking its the motherboard, but I can't think of why it would burn all of a sudden...

Any advice?

Windows XP Pro SP2
HP Pavillion 7560n
Athlon 64 X2 (W) 4200+ 2.2 GHz
GeForce 6150 LE chipset
Asus A8M2N-LA mobo
WD 3200JS hard drive
Nvidea GeForce 8400 GS