Something I found useful to know and that will avoid a reboot:
When working with Windows 2000 Server and external DNS entry changes, you may notice that Windows 2000 does not see the change if you have previously resolved the domain name. This happens because the server will cache DNS information so that the lookups are faster for any future requests that are made. The quick fix for this was to reboot the server.
However, the correct way to solve this problem is to use the features of ipconfig. By typing ipconfig /displaydns at the command prompt (append |more for a step-through list), you can view a list of DNS entries Windows has cached. The command ipconfig /registerdns will refresh all of the entries in the resolver cache. The entries will be updated and the server should reflect the appropriate updates. You can also dump all of the cache by typing the command ipconfig /flushdns.
It is worth noting that the entries should have a TTL, which would eventually expire. However, for frequent DNS changes this info is very helpful.