Download Squad has some good tips to improve iTunes for Windows. The post mentions several useful add-on programs, including iTunesKeys and idleTunes.

idleTunes has a host of useful features:
- find and insert album artwork into tracks
- copy iTunes playlists to any MP3 player
- export iTunes playlists as M3U, PLS, or B4S
- remove "dead" tracks from your library
- create playlists for all of the albums in your library
- create playlists for all of the artists in your library
- delete user playlists

By far the coolest feature of idleTunes is the way that it makes iTunes compatible with non-iPod portable music players, including intelligently renaming files when copying a playlist onto a screenless flash player to ensure the play order stays intact. Brilliant! And did I mention it’s free?

Finally, no post about how to fix iTunes would be complete without some directions on how to clean up your library and get consistent ID3 tags. For that, I'll direct you to Connected Internet, who has a great primer on how to use MusicBrainz Tagger to rationalize your music collection. It takes some time, but MusicBrainz makes it as quick and painless as it can be, and the results are definitely worth it.