This operation has been cancelled due to restrictions in effect on this computer
You can download a CMD file that can automaticly fix this for you here:
Click here to download and run the fix file. (on Windows 7 or Windows Vista, run this file as Administrator)
If you want do the manual steps to fix this problem, just run the following commands (Open Commando prompt as administrador on Windows Vista or Windows 7)
REG ADD HKEY_CURRENT_USER\Software\Classes\.htm /ve /d htmlfile /f
REG ADD HKEY_CURRENT_USER\Software\Classes\.html /ve /d htmlfile /f
REG ADD HKEY_CURRENT_USER\Software\Classes\.shtml /ve /d htmlfile /f
REG ADD HKEY_CURRENT_USER\Software\Classes\.xht /ve /d htmlfile /f
REG ADD HKEY_CURRENT_USER\Software\Classes\.xhtml /ve /d htmlfile /f
After this just make your Internet Explorer the Default browser.