I'll cite a fine example of MOVEONBOOT here. Why can't Microsoft remove these pests without the user having to help?
Windows Live Safety Center scanner may not be able to remove viruses stored in container files in certain folders
A blog from Live Safety Center team:
"Hello Safety Center Community, recently we've had several posts regarding certain viruses and threats that were detected but could not be removed. Brandon, graciously suggested turning off the Windows automatic restore point and re-running the scanner as a way around this issue. We investigated the solution because it seemed to be working in some cases. It turned out that in cases where threats are stored in the System Volume Information\_restore* folders they cannot be removed unless the system restore service is turned off. To turn off system restore read the support KB article http://support.microsoft.com/default.aspx?scid=kb;en-us;310405. If turning off system restore does not work or solve the problem, it could be that the threat is in a container file, we have found that in some cases we are not able to repair threats stored in container files. "