By default, the DNS Client service ("Dnscache") is enabled on Windows 2000/XP, so DNS lookups are cached locally for a certain period of time - set by TTL (time-to-live). This speeds up the process of looking up domain names. Windows 2000/XP caches successful ("positive") DNS lookups, and also unsuccessful ("negative") DNS lookups. The downside is during TTL, if an IP for an URL changes, problem occurs.

PHAS Windows 2000/XP users are experiencing intermittent connection timeouts and failures. Since disabling "negative" DNS caching does not work, the next step is to disable the DNS Client service.

According to Microsoft, if the DNS Client service is turned off, the computer can still resolve DNS names by using the network's DNS servers. See http://support.microsoft.com/kb/318803

Nscd is a *nix daemon that caches DNS lookups. The configuration file, /etc/nscd.conf, determines the behavior of the cache daemon. By default, nscd daemon is disabled (Could someone please confirm this? Thanks!). That's why *nix systems do not experience the same DNS lookups issue as Windows 2000/XP (Feel free to expand on this).

Disabling the DNS Client service on Windows 2000/XP:

1. Download sc.exe and dnscache_off.bat
2. Save both sc.exe and dnscache_off.bat on your desktop
3. Double-click on dnscache_off.bat
4. Delete sc.exe and dnscache_off.bat

Disabled the DNS Client service ("Dnscache") on the following workstations:

1. wxp: clerk3 - 20070123
2. wxp: headsec - 20070122
3. w2k: p120-12 - 20070118
4. w2k: clab20 - 2007???? - noisy fan
5. w2k: clab13 - 20070118
6. w2k: clab15 - 20070118
7. w2k: clab17 - 20070118
8. w2k: clab14 - 20070118
9. w2k: clab11 - 20070118 - fuzzy display
10. w2k: clab18 - 20070118
11. w2k: clab16 - 20070118
12. w2k: clab19 - 20070118
13. wxp: mantis - 20070118
14. w2k: clab12 - 20070118
15. wxp: jmolar - 20070118
16. wxp: turrell2 - 20070117
17. wxp: mshop2 - 20070117
18. w2k: clab18 - 20070116

Reference(s):
DNS Resolver Cache
How to Disable Client-Side DNS Caching in Windows XP and Windows Server 2003
nscd(8): name service cache daemon
How to flush DNS cache in Linux / Windows / Mac
Oliver Sturm's weblog - The DNS Client service riddle
The Elder Geek - DNS Client Service