I have to agree with Luke.  Sometimes the best thing you can do is an organized re-install.  I know it takes a long time, but many time you find models that you just no longer need.  Overall the new performance gain in loading your runtimes over time should more than make up for the few days of re-installing.  I probably do a re-install once a year though.

Shawn McCarthy
www.defyallchallenges.com