This is the note that I had from the link below...
[[Note The version of this tool delivered by Windows Update runs in
the background and then deletes itself. If you would like to run this
tool more than once a month, use the version on this Web page or
install the version that is available in the Download Center.]]
On-line version of the Malicious Software Removal Tool
http://www.microsoft.com/security/malwareremove/default.mspx
I do not know when that one was dated.
Updated: April 11, 2006 version reads...
[[Note The version of the tool delivered by Microsoft Update and
Windows Update runs in the background and then reports if an
infection is found. If you would like to run this tool more than once
a month, use the version on this Web page or install the version that
is available in the Download Center.]]
On-line version of the Malicious Software Removal Tool
http://www.microsoft.com/security/malwareremove/default.mspx
<shrug> Who knows? Maybe the Shadow does.