[Callum]

You say that Windows Media Player won't recognise them as part of the album? (Obvious... but just in case) Have you tried entering the album details manually in WM? Try right clicking on each file > properties > summary tab

Then enter all the details yourself...

However, if WM does recognise the files as the same album, and it is only explorer (that window) that doesn't, then do the following. In WM, click Tools > Process Media Information Now.

That should update your files...

Hope that helped...