Windows 7: database files

I am importing WMP database files from XP into Windows 7 WMP but getting an error message 'WMP doesn't recognise the wmdb file extension.'

This is baffling as it is an extension exclusive to WMP so how can it NOT recognise its own files?

Are MSN organising my music as they want it, not how I wish to use it? I cannot understand why it keeps changing the files, folders and tags and making all my single tracks into albums. Does anyone know how I can organise WMP as I want it? And why it won't recognise imported database files and playlists?

any help gratefully received

I've had problems with this before (wmp). I deleted the old database (not the songs!) and just reindexed the library afresh.