From: http://www.windowsitpro.com/article/dns/how-can-i-view-and-clear-my-dns-cache-content-.aspx
A. When a Windows XP or Windows 2000 machine queries a DNS server, the response is either positive (a match was found) or negative (no match was found). The OS stores these results in a local DNS cache so that local clients don't repeatedly query the DNS server for the same address. These DNS cache entries are known as DNS resource records, and the DNS resolver always checks the local cache before it queries the DNS server.
To view the current DNS resolver cache content and the entries preloaded from the Hosts file, go to the command prompt and type
C:/> ipconfig /displaydns
Each entry shows the remaining Time to Live (TTL) in seconds. To clear the cache, go to the command prompt and type
C:/> ipconfig /flushdns
Flushing the DNS cache clears all entries and reloads the entries from the Hosts file.