I have a Vista and also a cloned vista for backup.

After about 4 days something happened so I booted from the old vista.
About 50% of the files on the new vista got copied over by the old
vista. Why does this happen?

Strangest thing was my email (thunderbird). The email files got
SWITCHED! The old went to the new and vice versa. That isn't easy to do.

I also lost my nice new desktop and several new files and organizational
things I'd done on the new vista.

Is there a way to prevent this? I guess I could just unplug the new
drive when booting from the old but it defeats the purpose of backup.

John