Hi. I had a desktop built for me by a friend a while back. Recently the comp froze and when I tried to reboot my graphics card didn't work so I switched to my onboard. That is the old unsolved problem. After that my comp would always restart itself, programs stopped working and now my computer will only turn on for a few seconds. I believe my PSU is the problem but with the lack of cash I have I would like an expert opinion before I start buying replacement parts. Also, the fan and light on my graphics card still comes on but comp doesn't recognize it. Could a new, higher output PSU fix the problem? Thank you in advance for the help and I apologize for the lengthy paragraph.

Re-seat everything power connections from the PS to the board, drives and fans. Re-seat memory and CPU then see what happens.