well, first off, with your pc being an HP (factory) ... what is the model number of your system... like HP 5100 .. something like that...
it might be that you would need a certain type to fit the (PC tower) ... unless a standard PSU can fit...
also, that's pretty cheap for a PSU that was recommended above... you don't want to go real cheap.. you would end up in the same situation you are in now....