Go here first:
http://support.microsoft.com/kb/890830 If that doesn't help:
How to receive support
No-charge support is available for home users by calling 1-866-PCSAFETY in the United States and in Canada. For international users, contact your local Microsoft subsidiary. For more information about how to contact your local Microsoft subsidiary for security update support issues, visit the International Support Web site:
http://support.microsoft.com/common/international.aspx