What happened to my backed up data?

Episode 1047 (53:12)

Bob from Riverside, CA

Bob's 2006 iMac needed updating, so he installed OS 10.6 as a clean install, but the updated files didn't seem to install. Can he revert back and find his data? Leo says he could because it doesn't touch the data. Unless he erased the drive, and in that case he would need a file recovery utility.

Bob says he did copy the files over to an external hard drive first, but he says the newest date on the files is 2010. Leo says not to worry about the dates on the files. They could be creation dates not modification dates.