Windows Home Server
I was fortunate enough to be accepted to beta-test this ...and I gotta say it's doing it's job extremely well. I have 4 computers [Vista and XP Pro], all networked to the HomeServer. I have it set to auto backup all files on all computers, which it does once a week, or you can set it to do it more frequently. So far, every backup has gone without a hitch.
I'm using it on an older tower, with much of the hardware 2-3 years old or older, and everything works, and works well.
Microsoft is definitely working diligently on this one, and there's great feedback for it on the HomeServer forums, with all mentioned serious bugs being looked at and fixed promptly.
This is the one to get, for those with multiple computers. Just great! 