obviously what ran in your computer had administrator rights so I'm thinkin u allowed it to run (probably not known it) what's the error message it gives u when trying to change to fast Switch User?
U can also try and change the registry which is the highest authority in Windows
Warning: Modifying the registry could crash your system down to unrepairable causing u to lose data and maybe even havin to format the Hard Drive
I got u the address on how to edit the registry for this:
http://www.pctools.com/guides/registry/detail/973/
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