iTunes library is empty, yet iPad Music library is full of music

I recently replaced my PC, and since then my music hasn't played well from my iPad. All the music I had originally added from the old PC is still listed on my iPad (although not downloaded) and I cannot get anything from iTunes onto it.

Ideally I'd rather wipe all those album references from the iPad, rebuild my music library from my MP3s, and sync those onto the iPad. Any thoughts on accomplishing this? So far I can delete them one album at a time, but with 500+ more to go I'd like to get this done before the month is over... ;-)