Cause
The add-in was installed under another user account and the OfficeLive registry subkey necessary for that checkbox entry to be logged in the registry is not created for other users. You need to manually create the OfficeLive subkey under HKEY_CURRENT_USER\Software\Microsoft for any user on that computer that wants to suppress that add-in by checking the box. After the OfficeLive subkey is created the appropriate registry entry FirstRunDontShow will be created once Word, Excel, and PowerPoint are started and if the checkbox is selected it will no longer show on subsequent launches of those applications.
The issue can be resolved by adding a base registry key named OfficeLive under the HKEY_CURRENT_USER\Software\Microsoft subkey, once that key has been created the next time you start Word it should create two new DWORD entries (FirstRunCredsDeleted and FirstRunDontShow), both set to 1.
Solution
Install Office Live Update 1.4
OR Registry FIX
Steps:
WARNING : If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.
1. Logged in as the user that has the problem, click on Start, clcik Run, type regedit, click OK.
2. On the left pane expand HKEY_CURRENT_USER, expand Software, select Microsoft.
3. From the Edit menu point to New and select Key.
4. Type OfficeLive and press the Enter key.
5. Close Registry Editor.
6. Start Word, Excel, or PowerPoint, you'll get the prompt, make sure 'Do not show me this message again' is checked, click Continue.
7. Close the application (Word, Excel, or PowerPoint), the registry DWORD values should be created under OfficeLive for that user.