Hi! I have a late 2008 iMac (21", 2.66 GHz Intel Core 2 Duo, 2GB RAM, OSX Leopard 10.5.8.). I recently decided to install Snow Leopard and wanted to make a backup with Time Machine in case something goes wrong with the installation. I bought a 500 GB external Verbatim hard drive and attempted to make a back-up copy on it. Unfortunately, every time I try to do that my computer crashes; a grey screen appears after ca. 10 minutes and I have to restart my computer. Do you know what might be the solution to this problem?