I have another user's library in my iTunes

Today I got a bit of a shock to open my iTunes on my Windows 8 computer to discover that another user's name was now showing... Along with their complete media library, from music, to television to phone messages.

Anyone else seeing this? It really is there, making me think that perhaps the cloud (where I assume this came from) and itunes may not be a very safe place to be.

I have the most recent version of Itunes installed.

 

I was thinking that

This did occur to me as I am in a public place. I had a Microsoft tech working on my system trying to install their boggled 8.1 upgrade (they couldn't) and perhaps along the way something else got screwed up.

I appreciate your feedback on what I also thought might be happening. this has never happened to me before, so I may have to try reinstalling some applications to ascertain that alll is well.

Thanks again.