Hello, I'm new(ish) to Macs, having not used them for the 12-13 years, but I've now moved back, to an iMac. One of my first jobs was to replace the standard 250GB hard drive with a 256GB Samsung SSD. I decided to use the old drive in an external enclosure for timemachine, so I can keep regular backups on a seperate drive. However, for some reason, having done the main backup, it now keeps failing on smaller backups. When it fails it is saying that the drive has been removed from the computer incorrectly - Even though I'm not removing it at all. I have a feeling my OS X is making the drive sleep, right in the middle of doing a backup job. I could be wrong though. My iMac is a 20", with a 2.0ghz dual core, 3GB RAM, in the aluminium chassis. I'm running Snow leopard OS X. Any advice would be most welcomed. Thanks, Lee.