Well, after five years the old hard drive is on its way out. I have a new Seagate 750GB 7200 rpm to replace the 200GB one. I need to replace both fans anyway as they are loud, and going to replace the thermal compound as well. Basically, going to go through it. Hope it works when I am done. I now have Lion as my OS and no disc obviously as it was downloaded. So, do I just replace the hard drive and install Snow Leopard, and then Lion afterwards? I have the hard drive backed up on a Time Capsule, but does it back-up the OS (i.e. Lion). My iMac hard drive just failed under warranty and the Apple Store put Lion back on it when they returned it. So, I did not have to do any re-install of the OS. I just restored everything else off the Time Capsule. Thanks in advance.