[Imp]

Well despite you sayng so it sounds to me lke you are stll instaling in a folder monitored by UAC. Sounds stupid but you are installing the patches to the same folder as you installed the game to.

Turn off your virus checker
Install game & all patches in order to a folder say C:\Games\SPMBT
If I was you I would also turn off UAC
Open up Control Panel, and type “UAC” into the search box top right or google turning off UAC if that does not work.

This does make your system fractionally less secure but honestly its a total waste aimed more at placing stuff in set locations for business IT guys.
If your really worried about security you should not be using your adminastrive account as your day to day account

If this does not work can only suggest you may have a virus