I use registry cleaners. I think it helps to keep old outdated entries cleaned out. I run a reg cleaner every few months. But I install and remove a lot of programs. If you're someone who rarely installs and removes programs it wouldn't be needed as much.
MS has made a reg cleaner for years but it may just be for Win9x not 2K, I don't know. There are also several programs made by other companies that do a good job. For Win9x I use the MS version and another one called Reg Cleaner 4.3 from
www.jv16.org there are also others out there.
Here is a free one that works on Win 2K
http://www.pcmedixwebs.com/regclean.htm