If you don’t want to look for a solution, but just want to solve the problem, insert this key in your registry to suppress the notification:
[HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Excel\Security]
“ExtensionHardening”=dword:00000000
You can accomplish the above by doing the following:
- Open your Registry (Start -> Run -> regedit.exe)
- Navigate to HKEY_CURRENT_USER\SOFTWARE\MICROSOFT\OFFICE\12.0\EXCEL\SECURITY
- Right click in the right window and choose New -> DWORD
- Type “ExtensionHardening” as the name (without the quotes)
- Verify that the data has the value “0″