It seems likely to me that this is the result of the massive success of Windows 7 - users are just upgrading from XP where they may have been using Firefox or C

It seems likely to me that this is the result of the massive success of Windows 7 - users are just upgrading from XP where they may have been using Firefox or Chrome after a friend/relative/coworker suggested they switch and are now using the default Win7 browser: IE8.