Mike - my gratuitous two cents:
Not to start a family squabble here, but unless you have noticed
bothersome (serious) performance degradation there's usually no need to
reinstall an OS like W2k. Other things you can look at are adequacy of
your system partition size, of your pagefile size and placement, and of
the space taken up by unnecessary temp files and directories. Regular
defragging of all partitions, including of syatem files and indices
therein, can also help. You might also check to see how the "max
registry size" setting compares to the current size of your registry and
adjust if necessary. (Fragmented registries, pagefiles, and file indices
like MFTs and directories can slow down a system noticeably but are
easily fixed with a good defragger.)
The mother-wit adage If It Ain't Broke Dont Fix It is generally good
advice for most folks. Although NASCAR guys treat motors like you and I
treat shoes, most people are satisfied with an occasional tuneup down at
the corner garage. There's a point at which the next 10% performance
improvement doubles your cost in time and energy. Tradeoff time. If
you're a serious gamer, though, you may be more like the NASCAR folks.
In that world, extreme tweaking and overclocking are the norm.
You will find the "If it ain't broke..." vs the "Periodic reinstall..."
arguments a long-running debate where there's truth on both sides. Kind
of like the PC/MAC clash, but more muted.
Heavy internet use may mean large bookmark files; if you do reinstall,
make sure you capture all that kind of thing too.