WIN2K Pro registery

I have several machines with WIN2K PRO that are begining to boot slow, run slow and take for ever to shut down. These machines are not producing errors, just running slooooooow in general. They have been in use for 2 1/2 to 3 years with no maintenance except defrag and disk clean up, so I know there is a lot of "junk".

Any suggestions on a registery checker and registery clean up and other general "tune up"?

Thanks!!