Windows XP stores a cache for all DNS answers, either negative or positive.
Positive caching is somewhat useful but i think that negative caching is evil, it really makes no sense for me.
Developing web applications using multiple networks and multiple local DNS server sometimes can happen that your box receive a negative DNS answer and you aren't able to get the correct local resolution.
You can clear the cache with "ipconfig /flushdns" but sometimes this not works so a DNS Client Service reb...