We have an old media center PC that my wife used to have as her primary machine, before we bought the MacBook. It's still got a lot of photos and other stuff on it though, so losing the Hard Drive would be a problem. Given how often we have little micro-outages, we bought a UPS. At the same time, we bought a MyBook terabyte drive to use for backups. We hooked everything up, restarted the PC - and nothing.

Hmm. It wasn't getting to the hard drive (i.e., not booting) at all. So, we unhooked the UPS, tried again. No boot. Unhooked the MyBook, booted - came up. So - to recap - the Windows machine was apparently trying to boot from the new USB drive. Why it would do that, I have no idea.

And people wonder why I like Macs :)