First of all, I apologize for posting a Windows XP question in the Windows 7 forum, but the XP support forum responses, one by a MS Support person, both directed me here for my answer, and the only current XP forum in TechNet is specific to the installation of SP3. Over that last two months, I have run Windows (XP) Updates manually on many of my clients' Windows XP Pro systems that had gotten somewhat behind on updates (~100 - 200 MB per PC, critical & optional updates combined), and some of them have lost some DNS client functionality. Out of perhaps 75 computers updated, five have had this problem, but it is quite severe when it occurs. Specifically, after the updates, these things fail: IE8 (404, page cannot be found), cannot resolve DNS names when pinging, domain login script does not run, and cannot access resources on network shares. However, in every case, nslookup does work to resolve names, I can ping LAN and Internet IP addresses, DHCP client works fine, and I can open websites and network shares using their IP addresses instead of URLs. In NO case has any of the following resolved the problem: netsh int ip reset, netsh winsock reset, netsh winsock reset catalog, manual removal of the winsock registry entries & subsequent reinstallation of TCP/IP. In one case, one of the MS Fixits (50202 or 50203, I believe), resolved the issue, in another, the winsockxpfix EXE worked. In two cases, both of these also failed, and I was reduced to running a Windows XP repair installation. I have one more in front of me now for which my last resort will also be a repair installation, but I suspect there is a solution targeted on the specific TCP/IP issues. How can I test to determine the specific file or function that is failing so that I can (hopefully)resolve this issue without a Windows repair installation?

Thank you for the response. None of the computers have Bonjour service because I tightly control what goes onto all my domain computers and do all installations adminitratively. I have already been through the winsock reset instructions, including the link you provided, from several angles. What is most odd is that it seems to affect only certain portions of DNS: nslookup, which relies on DNS, of course, works perfectly, as do pinging LAN or WAN hosts by IP address, presumably ruling out any type of routing issues. However, domain access (logon scripts, shared folder mapping) does not work, presumably because at some level, the services cannot resolve the name of the DC, which is also the DNS server. It is very strange that nslookup can correctly communicate with the DNS server, but ping, IE, and domain-based services cannot.