My uncle used to keep his laptop and desktop synced. He stopped doing this a while ago for various reasons, but only turned off syncing on his desktop. Last week he took his laptop across country on a trip, and at some point got a message "Synchronization complete." Desktop at home was turned off so there was no chance of some random connection back to it.

I asked him what program he used to sync the two and he replied it was XP's built-in sync program. Both computers use XP.

He's a bit concerned that his computer may have been hacked. I doubt a hacker would use such an obvious method, but are there any other ways his data could have leaked that would give this message? Or not give this message, for that matter?