Probably something hosed in your User Account. You could log in to a test account (create it if you don't have one) and see if it has the same problem.Interestingly, that was already checked off, along with many other items that are not showing up in the sidebar. What is wrong?
Correct!No, no, don't delete Preferences folder - just com.apple.finder.plist.
Finder will be set, after Mac reboot, to its default settings (like it was when first booting into new OS X).