So for the first time ever I power on my iMac and get a flashing folder indicating the system cannot find the boot disk. I reset it a few times and it eventually boots up. A few days later the same thing happens only this time I can't get it to boot up after many attempts. I try all the usual suspects, reset PRAM, attempt to select boot device (can't find any) Finally I boot from the install CD and when I get to select a destination volume for the OS there are no volumes to select. I shut it off for a few days assuming I'd need to take it to an Apple store for some kind of repair or hdd swap. However it just started up tonight when I passed it and decided to hit the power button. Should I do anything to it while I have it running? Would a fresh OS install do anything for me? I have everything backed up with Time Machine.