Troubleshooting Microsoft Core XML Services 6.0 / 4.0 SP3 3 Issues

Troubleshooting Microsoft Core XML Services (MSXML) 6.0 and 4.0 SP3 often centers on resolving installation failures, security patches, and application errors related to parsing XML documents. MSXML 4.0 is outdated and often presents security risks, while 6.0 is the more secure, modern standard. Common MSXML Troubleshooting Steps

Error 0x80070490 (Installation Failure): This often occurs when installing MSXML 4.0 SP3 (KB2758694). To fix this:

Download the update directly from the Microsoft Update Catalogue. Right-click the .exe file and select Run as Administrator.

If it fails, use the Deployment Image Servicing and Management (DISM) tool to repair system corruption by running Dism /Online /Cleanup-Image /RestoreHealth in an elevated Command Prompt.

Security Vulnerabilities (Unsupported Version): Security scanners may flag older MSXML versions.

Solution: Upgrade software applications that depend on MSXML 4.0, as it is no longer supported. Upgrade to MSXML 6.0, which follows the support lifecycle of the operating system.

Failed DTD Requests in MSXML 6.0: You may see errors when loading XHTML documents if Document Type Definition (DTD) requests are blocked.

Solution: Install the latest updates for MSXML 6.0, which allows caching of DTD files locally and resolves validation errors.

Removal of MSXML 4.0 SP3 Security Updates: If a security update fails or needs to be removed, it may not uninstall cleanly because it uses a side-by-side (SxS) installation mode.

Fix: Remove the security update (KB925672) via Add/Remove Programs, then manually delete msxml4.dll from %SystemRoot%\System32. Troubleshooting Checklist

Run as Admin: Always run installers for MSXML 4.0/6.0 as an administrator, particularly on Windows Vista, Server 2008, or later.

Repair/Reinstall: Use “Add or Remove Programs” to repair existing MSXML installations if parsing errors occur in applications.

Check System32: Verify that msxml6.dll or msxml4.dll exists in the System32 folder.

If you can tell me what specific error message you’re seeing (like the error code or a text message) or when it happens (e.g., while installing a specific app), I can give you more tailored troubleshooting steps.