yeah, as long as you don't have a dell or some other name brand pc. if you do you can't just buy a new psu off of newegg or something and put it in and rock on, you'd have to buy it from the company and pay an arm and a leg for it.
But yeah, if you have a custom pc then you can just buy a new psu and swap it. Depending on what components you have, I'd go with a 400-500 watt psu. And brands like thermaltake, aspire, antec.