I have a late 2007 20" Aluminum iMac with a 500GB hard drive and I need more space. I have looked at the how to replace the HD and don't have any questions with the physical replacement. I am just really scared of getting my software back onto the new drive. I am looking for a larger, 2TB to 3TB drive that is faster than what I have. I think mine is 5400rpm so the new ones with 7200 should speed things up. A SSD would be faster but I need more capacity. I am very nervous about the formatting and getting going again. I do have a Time Machine back up connected but I am just not sure what to do with the software. Is there someone that can tell me what I need to do after I have done the physical replacement?