Here's what I'd do:
At this point, I suspect that you are unable to either install, or
uninstall, Microsoft Antispyware--is this true?
The control panel, add or remove programs, Microsoft Antispyware has two
update options--one reached by Change, Update, and another reached by "click
here for support information", Repair. Do either of these work and help?
If none of that avails, here's what I'd do.
Download the Windows Installer Cleanup tool:
http://support.microsoft.com/default.aspx?scid=kb;en-us;290301
Delete the Microsoft Antispyware installation folder and all subfolders.
Typically, this is c:\program files\microsoft antispyware.
Use the Cleanup tool to remove the Installer information for Microsoft
Antispyware.
Once that's done, be sure that you are logged in as the administrator who
will be using the program, and reinstall the current version--1.0.615.
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