Update for Microsoft Windows XP
This update resolves a problem in which authentication fails when you either use Microsoft Outlook or Microsoft Outlook Express to try to log on to a HTTP-based mail server.
http://support.microsoft.com/kb/904942/

Microsoft Windows Malicious Software Removal Tool
The Microsoft Windows Malicious Software Removal Tool checks the computer for infections by specific, prevalent malicious software.
http://www.microsoft.com/security/malwareremove/default.mspx

Network Diagnostics for Windows XP
This tool helps you identify and fix connection problems.
http://support.microsoft.com/kb/914440/