Not sure about why it won't load (have you done an alt-ctrl-del and seen if it's hanging or not responding? any chance that it's minimizing to the systems tray?) but itunes on pc likes to store music in a folder called 'itunes'. I think mine was inside my My Music folder originally but I've since changed it to just be the My Music folder.

Have you tried searching your computer for a specific mp3 that is in iTunes? You may have to ask it to include hidden files/folders.