I now have a 500GB external HDD (WD Studio for those who care to know) to backup my 24" white iMac 250GB HDD. I have the WD Anywhere Backup program that came with it set up to backup any files, music, movies, and documents I've created.....pretty much anything in my "home" folder. My question: does it make any sense to use external HDD space to backup the rest of the HDD, particularly the applications, when I have the install disks for the original config, shelf copies for others, and copies of the .dmg files for those I've downloaded (i.e. MacHeist)??? or is that just a waste of space I could otherwise use to store files I don't care to have on both my iMac HDD and external?? I'm just trying to figure out if there's any real advantage. What do you Mac veterans do??? and why??