Machine Check Exception

Recently, I've been getting Machine Check Exception blue screens. Is this a hardware specific error, what is it, any ideas on remedy?

Asus P4PE
Intel Pentium 4 1.6 At 2.66
Samsung DDR333 (512, 256) At DDR443
Albatron GeForce4 Ti4200P Turbo
Creative Audigy
Realtek RTL8139
Maxtor ATA133 30GB
Sony CDRW
Windows XP Professional

do you get these errors at stock speed? can your computer pass prime95 and other stability test programs? also, what are your processor temps, and have they gone up recently due to the end of winter or dust?

Seems to run fine at default speed. Temperatures seem same. Almost everything over 100 FSB (default) brings that error message.