Our computer went out about 2 weeks ago (the cache memory went out) and so we replaced it with a new computer, but we had just purchased and installed a new hard drive 3 months previous. We would like to save our old hard drive and we were told that if we bought an enclosure for it then we can hook it up to the computer, retrieve our files and use it as an external hard drive. My question is I am not sure what size case to buy. I went online and looked at external enclosures and the sizes are 2.5 or 3.5, but when I measured our hard drive it was 5 inches X 5 1/2 X 1/2 ", so now I am not sure what size enclosure I need. If someone could help me I would appreciate that.