A quick and dirty but easiest way to solve this problem, is to insert the following registry key. This will simply suppress the notification:
The step-by-step instructions are as follows:
- Click Start, click Run, type regedit.exe and press ENTER. This will open your Registry Editor.
- Navigate to HKEY_CURRENT_USER\SOFTWARE\MICROSOFT\OFFICE\12.0\EXCEL\SECURITY
- Right click in the right window and choose New → DWORD
- In the Name field, type ExtensionHardening.
- Verify that the data has the value 0.