You may receive this error in various Windows programs, including Outlook, Excel, Word, etc., if you have installed alternative Windows browsers that take over the HTML open command, such as Chrome or Firefox. In my case I received the error message “This operation has been canceled due to restrictions in effect on this computer. Please contact your system administrator.” whenever I tried to click on a table of contents link in a Microsoft Word document. I solved the problem by changing the HTM / HTML association in the registry. Here is what you can do if you receive the same error.

1. Open Regedit and browse to HKEY_CURRENT_USER\Software\Classes\.html

2. Right click the value for the .html key and select Modify

3. Change the value from “ChromeHTML” to “htmlfile” (or from FireFoxHTML to htmlfile)

Repeat these steps for htm and .shtml keys if they exist. Check out also the xhtml and xhtm keys. Your problem will be fixed immediately (no need to restart Windows). Enjoy!