I think you need to edit the id3 tags so that they all say AC/DC. Right now you have ACDC, AC DC, and AC/DC. WMP thinks they're 3 different bands. Your best bet is to find a tag editor so that you can do them all at once. (You might be able to do it in WMP, I'm not sure because I don't use it. I use WinAmp and I know that you can do it there.)