Hey, I too was victim to this situation, and was reluctant to do a clean install just to regain the functionality of Windows defender built in to Vista (unknown to me), as with all prior versions you were able to uninstall and reinstall as a stand alone program. After finishing the Vista premium upgrade my anti-virus program recommended to turn it off (as it has spyware scanning built in) so I figured why not uninstall....right! Wrong! I should have done some research first, but to make a long story shorter, all you have to do is set 3 hours aside, when you have the time and run the setup off of the Vista installation DvD from the Vista desktop (do not boot from the DvD or a clean install is your only option), this way the program installer will let you repeat an upgrade retaining all your info you have as it did in the original upgrade. The only down side is like I said earlier you have to wait out the rather long installation process again. It worked like a charm for me.
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