Backups should happen every few DAYS. Not weeks or months. I mean the automatic backups, not manual ones. Check your backup directory again. You're probably missing something.
This is yet another reason to set "fix broken links" to NO. It's the safest option that gives you the most control.
You might also want to look into forcing Windows to assign a drive letter to your primary drive and keep it.
Finally, if you are forced to re-import your library, you shouldn't lose too much. Mainly things like import date and maybe play count. As long as MC has been set to write tags back to your files, you should have the vast majority of your metadata stored in the song files themselves.
Brian.
