Grey screen, wiped mac and still same problem

Question

About 2 weeks ago my son accidentally pulled the power cable out of the back of the iMac. He then suffered quite a bit of freezing on several applications and even force quit was not working. He had to hold the power button in to turn off. He then had quite a bit freezing but force quit was working, albeit quite slowly. One day I could not login to my user account, my son had his open and the shared account we use for the iPad and I thought this might be causing my account to start logging in but just ending up back at the login screen. I logged out of the other two accounts and tried again and it worked. It was fine for a few hours but then I logged out and later my son tried to log in to be met with a grey screen and spinning cog. After looking on line we first tried safe boot which worked but then after restarting the same grey screen. It then seemed that we should insert the cd and try disk repair but this was greyed out so we could only verify disk and then the disc would not eject. I couldn't eject from the keyboard or from utilities but finally did it from starting up and clicking left side of mouse. After quite a few more start ups where we had grey screen followed by blue screen then nothing we then got it to start up. I quickly backed everything up using time machine and tried a repair disk again. This time it said the dusk could not be repaired so we prepared to wipe the iMac. I did this with relative ease until an error message showed the installation had failed. Back to the Internet for more help. Verbose mode threw up an error message of disk02 i/o error so we started again with doing a reinstall. It worked and seemed ok for a day or so, then freezing, spinning beach balls etc. I tried a verify permissions and about 50 needed repairing which it did. Worked fine and we started to copy our music and photos back (I don't actually know how to bring back everything but we were running out of space anyway so it seemed ok to just bring things back slowly). It seemed ok though start up was atrociously slow even with nothing on the system but it was working. Then Christmas day and my son has a new iPod which he wants to sync. It starts up fine, he syncs and then turns it off for Christmas lunch. He turns it back on and grey screen but this time nothing else, it can sit with spinning cog for over 10 mins. We've tried the power supply trick, draining the power and waiting but nothing. Is it the hard drive? And if so is it worth repairing or should we be thinking about a new iMac?

Answer 1

Update on my iMac, apple rang today to say they have replaced the hard drive too and let it run on and off since Saturday as the problem was intermittent and they had to make sure it did actually boot up properly. Anyway it seems the pulling of the cable from the back of the iMac caused a power surge which in turn caused problems on the hard drive, I have been saying this since day one but no one would listen! Apple are replacing the hard drive free of charge as they have caused us some inconvenience in not fixing it properly first time. That's what I call excellent customer service.
Quatchi, it sounds like there are similar issues on your hard drive to ours, apple said bad sectors and I'd guess you'll need to replace the hard drive.
Message was edited by: GG31568