Originally Posted by testman
I hope my mobo hasn't taken any damage. Should I stay at 300w or get something higher?
Watts are what the ill informed view. Your concern is current for each voltage. For example, if the orignial 12 volts was 22 amps, then your new supply must also do 22 amps or higher.
In a market where so many computer assemblers know nothing about electricity, then many supplies missing essential functions are dumped into the market. Naive says a computer boots. Therefore that supply is fine. Nonsense due to insufficient knowledge. Essential functions are why power supplies cost at least $60 retail. Why a $25 supply can boot a computer - and be missing essential functions.
If your supply was from HP, then it would not damage the motherboard. One function so easily 'forgotten' when selling a cheaper supply with more watts to the naive.
It is the supply? Buy or borrow a multimeter to have an answer in less than a minute. (A meter typically costs less than a hammer.) Or just randomly replace parts until something works. Those with superior knowledge could say nothing because hard facts and numbers were not provided. Those without electrical knowledge will simply recommend shotgunning.