Here is a step by step tutorial to get rid of this message:
Click Start>Run and type gpedit.msc
. Click OK.
Go to User ConfigurationAdministrative Templates Windows Components
Double-Click on "Inclusion list for moderate risk file types
" setting and click apply.
" to the "Inclusion list for moderate risk file types
" setting. You can also add other file types.
This should disable the "Publisher Could Not Be Verified" messages from appearing for that file type in the future.