Right-click the file you need to install, & on the General tab, click on the Unblock button.
If that doesn't work, look under the Security tab (as above) & see if you have the necessary user permissions to run/open the file.
If still no joy, Norton2010 could have added another layer of security. Disable this in Norton's options. Or, there may be an option on the right-click file or right-click file > Properties. G