iMac making grinding noise

[Rug]

My 20 mo. old 24" iMac has started making a random grinding noise. My guess is it's from the hard drive. Any advise?

[djackmac]

Very well could be if the noise is not consistently happening all the time. Could also be the optical drive if happening with CDs or DVDs. May even be something in one of the fans if the noise is more constant. Best advise I can think of is back up your data to be safe in case of a hard drive failure.