Hi there, please read the known issues here:
http://support.microsoft.com/kb/954430
If appropriate either manually install the update or seek assistance from MS
regarding the update.
"To work around this problem, manually install the security update from the
Microsoft Download Center, and then click Ignore when the error message is
displayed. To confirm that the installation was successful, verify that the
version of the Msxml4.dll file in the %SystemRoot%\System32 folder is
4.20.9848.0."
"How to obtain help and support for this security update
For home users, no-charge support is available by calling 1-866-PCSAFETY in
the United States and Canada or by contacting your local Microsoft
subsidiary. For more information about how to contact your local Microsoft
subsidiary for support issues with security updates, visit the Microsoft
International Support Web site:
http://support.microsoft.com/common/international.aspx?rdpath=4
North American customers can also obtain instant access to unlimited
no-charge e-mail support or to unlimited individual chat support by visiting
the following Microsoft Web site:
http://support.microsoft.com/oas/default.aspx?&prid=7552
For enterprise customers, support for security updates is available through
your usual support contacts. "