Hope its ok to post this here but didnt know where else to go!

Nothing was out of place last night, I shut it down as usual everything was working fine.  This morning I turned it on then went to get a drink while it was booting and come back to find that everything has reset itself to default.  By this I mean that the Start Menu is back to blue where I use the silver, the frequently used program list is empty, my bookmarks are gone just like I had restored the computer but all my programs are still working....   Nobody was here to mess with it!    Oh it is a laptop if that matters any.

Now while everything appears to be working fine I am curious to know what might have caused this because in all my years on these things I have never had that happen!