iMac not booting from HD, cannot repair disc in Disk Utility
I've had the imac G5 for nearly two years and its been running without a problem, now it suddenly wouldn't start up. Firstly I get two or three grey screens in succession looking as if being drawn from top to bottom very quickly, then the apple logo and timer, after a minute or so the fans start up to full power and it stays that way.
What I've tried:
Reading around discussions I tried rebooting from DVD installer and using disk utility. Result: error message: The underlying task reported failure on exit. 1 volume could not be repaired because of an error.
Because I want to sell the imac I had backed up all of my important data so I zero-wrote the hard drive in preferrence to buying a third party repair package. Reinstalled from DVD. Shut down and restarted. Everything worked except those banding grey screens appeared that were never there before. Something looks wrong. Then when i tried to reinstall microsoft office (as a test) the OS seemed to freeze and I had to shut it down again. Now it won't boot up as before. This looks like a very serious problem.
I hesitate to buy tech tool pro in case that doesn't solve it either.
Can't think if I did something to cause this. All I've been doing is transferring some data via ethernet to a newer mac. There was also a Lacie firewire drive linked to both computers as i was backing up stuff. One night I shut the iMac down and the next day it started with this problem.
Well... any educated suggestions would be most welcome,
thanks.
By the way, the memory in the mac was purchsed from a third party and installed ages ago by myself. Never been a problem with it and have been running Final Cut Studio no trouble.
iMac G5 2GHz Mac OS X (10.4.7) RAM 2GB