Mac Pro G5 Tower Will Not Boot

While using my Mac Pro G5 tower, the image on monitor suddenly fragmented. Then I got the colored rainbow wheel of death. There was no response, so I was forced to hard shutdown. When I tried to restart, I got the gray Apple screen and the spoke wheel of death (black and white). Then it froze (stopped spinning) and the computer won't get past this to complete boot. I assumed it was a computer issue, so I plugged in an old (1999) G4. It worked fine for a few minutes, then did exactly the same as the G5 tower. So, I destroyed 2 computers in a few minutes and the problem was the surge protector power strip. I replaced to power strip, tried another G4 (2004) and it works fine. I don't care about the 1999 G4, but if there is a way to fix the G5 tower, please let me know. Thanks.