seem to remember reading somewhere they had been selling 500w psus as 750w
and even as a 500w it wasnt a good psu
stick to corsair,seasonic and other good brands
your whole pc relies on the psu so dont try to save too much on it
edit--heres a quote from hardware secrets
The Coolmax V-500 is a textbook example of why you should not buy a USD 20 power supply. Its inability of delivering its labeled wattage is not its worst problem. It presents lousy efficiency between 66.8% and 77.1%, its voltages are out of range, and noise and ripple levels are above the maximum allowed. A perfect weapon of mass destruction. Stay away.