Thanks for replying yep, I'm using WMP 10.
1) Basically it says first of all that it doesn't recognise the file type but it might be able to play anyway, then it says "Windows Media Player encountered an unknown error. This can occur when another program or operating system component encounters a problem but does not communicate the nature of the problem to the Player." and then it closes itself!
2) If i click a song to play on my desktop then sonicstage opens itself up but then doesn't do anything, it doesn't even register an error at all, just nothing, as if I hadn't clicked anything. But if I tell it to play mp3 files it comes up with "Omgjbox.exe has encountered a problem and needs to close. We are sorry for the inconvenience." then it askes me whether I want to send an error report.
3) Nothing that I know of, it wouldn't be a virus because I scanned my computer earlier and also I have a firewall, so it is unlikely to be that.
Thanks for your help