After uninstalling drivers for old vid card, USB ports...

Do not work. Basically, what happend was I ordered a 7600gs for a fairly old gateway, in an attempt to squeeze the last bit of life out of it before I built my new comp. I uninstalled old card's drivers, put new card in and mouse and keyboard wouldn't work. The PSU I have in the system was lacking, by a lot, in Wattage for the new card. It was dumb to try and get the card to work with that PSU. What I am thinking happend was, if this makes any sense, that the computer shut down all unneccersart functions to run in order to supply power to the new card. Would a new PSU allow the card to run, I sort of need this comp good to go, as I want/need to get back to my precious online games. Thankyou in advance for your help.