When I try to boot up my iMac (G5, built-in iSight, 1gb ram, 10.5.5.) it stalls at the black screen for about 15-25 seconds then the fan starts up loudly. I tried booting from the leopard install disc by holding "c" on the start up. It'll start to sound like the disc is getting read. I get to the gray apple screen with the pin wheel moving but, after about 15 seconds the fans whirls up, the screen becomes a darker shade of grey, and I get the "You need to restart your computer" kernal panic message. If anyone knows any possible solutions i'll really appreciate it.