I sorta had this issue when installing a new version of itunes on windows sometime ago. The playlists themselves are in some .xml file format and moved elsewhere. As for the actual music files, you'll have to check int he default directory for itunes if they're there. It should be in the Music folder and under Itunes\itunes Media. If it's not there then like Lgain Ablar suggested, check in the windows.old folder but I somehow doubt it will be there. Usually the installations or upgrade of windows unless you specify doesn't wipe out clean out your folders.