Robert Fripp recorded hours and hours of music, out of which Microsoft snipped about 4 seconds for the startup theme of Vista. There's a video about the whole process on Channel 9 here - which, if you want to think about things that way, rather puts the 'extravagance' of getting Bellowhead in to do the Archers theme into the shade ...

Oh, and Bellowhead and Vista in the one thread? Let the bile flow!