Vista - Windows Media Player problem

My Windows Media Player has been working fine since I got it and I spent hours sorting out album cover art etc. for the albums that hadn't got any.
Anyway one day I opened it and there was no music in the library. For no reason at all it all vanished. It now says: "There are no items in the library yet- the Player is searching for digital media files in the background. Click here to add files to the library now."
Obviously all my music is still on my laptop, and when I click a file individually WMP plays it for me. I've tried the "click here" option numerous times and tried to manually add the "My Music" folder but it does nothing once I click it.
It's really frustrating me now because I can't even uninstall and reinstall it. Does anyone have any idea what could be wrong? Any help is greatly appreciated!