To flush the Windows XP (and probably 2K) DNS cache, run this:
ipconfig /flushdns
OT: ipconfig /release && ipconfig /renew
See the cache: ipconfig /displaydns -- wait a bit and run again to see TTL counters count down.
Note that programs and other devices involved in your Internet connection like web accelerators, routers, and even your ISPs DNS servers have their own caches for DNS queries, thereby leading to significant confusion.
Add a third DNS server: (GUI only allows 2)
netsh int ipv4 add dnsservers "Local Area Connection" 8.8.8.8 [Google DNS]
Tool to benchmark DNS servers: https://code.google.com/archive/p/namebench/
Tags: domain name, reset, clear, cache, winxp, w2k