The PSU is probably a Shoddy ATX1 500W (probably only outputs 400w) i don't think it would handle your setup
Get a PSU thats atleast ATX2.0,500W output
I would recommend a SilverStone 560W(500W output) EF56F PSU its only $80US on Newegg!
Good luck!
Iam doing my rounds of thr THG forums today, got nothing else to do !