I've said before that I have a Mac computer. I've had Macs almost from the time they were introduced, and I haven't done a clean installation of a new operating system in at least ten years. As a result, there's lots of extra "stuff" hiding in various places on my hard drive -- stuff I no longer need or use. Given that, I decided it was high time to do a clean installation of Yosemite, the newest OS, on my Mac. Ouch! It's so much easier just to upgrade! I've been moving things, reinstalling things, discovering that data doesn't always just copy easily but must be exported, etc., etc. So far, I've been working on it for a day and a half, and I may have finished the worst of it at this point. I'm waiting for a couple of tech support replies, and I may still reinstall a couple of apps I haven't yet decided are vital, but the majority of the work is past.