post photo of PSU
it seems standby 5V regulator popped
I think its not due to over load. standby chip pop unknown reasons, power surge, faulty capacitors, etc..
If money is not a problem, get rid from that hot, power hungry, DX10 card and get GTX670/680 etc.
I think its not worth to spend money for that cards.
try to sale gtx280 and go for new one.
As topic says my friend's HD4870 (referance design) show whole screen full of artifacts when boot.
Tried with another PSU but same fault. so is it VRAM damaged ?
Baking card will fix it ?