Having spent a couple years at Microsoft in Premier Support (Big $ clients), their are no known problems with Windows 2000 requiring a regular reload, and by-design they don't want a product that doesn't work. Typically you may find a application with a memory leak, bug, etc creating a problem. In that case a qualified person can find the problem using the tools microsoft provides (checked builds, resource kit tools, etc) and the software code can be fixed. The hard part is finding a qualified person with formal and extensive Microsoft internal training, or getting the developer to check their code. If you can't find that person, then the common street strategy is fdisk, format, re-install, reload. These people solve the problem the same way if they are using Solaris, Linux, or Netware.
Although I sometimes wonder if my Catalyst 6500s would be better off with a regular reload (due to caveats)....I can understand the question as Cisco hasn't sent me to 6500 training, and I don't work on them all day/every day.
