Before resetting Internet Explorer to default settings, you may want to backup the ‘trusted sites’ in case they are deleted.
Just export this key and then after the cleanup, add the info back to the Registry by importing the key.
Open up regedit.exe through the start menu search or run box and navigate down to the following key:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap\Domains

Right click and export the key.