try to reset bios, both with battery and the jumpers (only using the jumpers dont help somthimes). (make sure you unplug the psu power cord before doing that)
and check if the mobo is correctly mounted on the spacers underneath it.
Then check if core on cpu is broken that can happen with a amd when mounting the cpufan.
Then if not working, try with one memory chip at the time.
I guess you have tried starting it up with only grapichcard, cpu and memory, not attaching hd`s etc.. that can also give a clue about what is wrong youre down to : cpu, mem, motherboard, psu then

GL ! I know how frustrating things like this is
