Biostar 6100-m9 rebooting problems

[Ka102]

My computer is constantly crashing under high load.

Ive replaced the ram twice,(i got 1.5gb now, thats a plus)
bought a new harddrive
and my videocard/CPU are brand new.

I'm 98% sure its my motherboard now, because ive searched and other people with this same board are having the problems, but i couldnt find any solutions

Anyone here know what i could do?

Edit
Specs:
Amd athlon 64 3700+ 2.2ghz Venice core
Kingston pc2700, 1.5gb
Antec 500w PSU
Ati Radeon x800
Biostar geforce 6100-m9