A repair installation might have been a little rush of a solution but it is usually a sure-fire fix for things like this. Usually, not always. There's nothing wrong with the fact that you went this direction.

The setup process won't find your existing XP installation if it's corrupted badly or if you're using a different version of operating system. I'd be surprised that the installation is in that bad of shape considering your only issue was with a printer related DLL file. So on the other possibility - are you using the same setup CD as your installed OS?

If you still have problems, you could simply boot back into your computer as normal and back your important stuff up. Then you could do a clean installation which would wipe your hard drive and install Windows from scratch.