When starting Office 2008 for Mac applications you receive “your product key is not valid” error message


After installing the latest Office 2008 for Mac update, every time that you start a Microsoft Office 2008 for Mac program, you experience one of the following symptoms:
  • The Office Setup Assistant runs unexpectedly.
  • You receive the following error message:
    Office for Mac has determined that your product key is not valid. To use Office for Mac, you must enter a valid product key.


This problem occurs if one of the following conditions is true:
  • Your copy of Office 2008 for Mac was installed by using an invalid product key.
  • Your copy of Office 2008 for Mac was installed on more than one computer by using the same product key.


To resolve this problem, you must remove the invalid product key, and then enter a valid product key for Office 2008 for Mac. To do this, use one of the following Methods below.

If you do not have valid product key, purchase a genuine copy of Office 2008 for Mac. To do this, visit the following Mactopia Web site:


Or, visit the following Microsoft Store "Office for Mac" Web site:


Method 1: Remove Office 2008 preferences

  1. Quit all running applications. 
  2. On the Gomenu, click Applications.
  3. pen Microsoft Office 2008, and then open Office.
  4. Drag the OfficePID.plist file to the Trash.
  5. On the Go menu, click Home.
  6. Open Library.
    Note The Library folder is hidden in Mac OS X Lion. To display this folder, hold down the OPTION key while you click the Go menu.

  7. Open Preferences, and then open Microsoft.
  8. Open Office 2008, and then drag Microsoft Office 2008 settings.plist to the Trash.
  9. On the Apple menu, click Restart.
  10. After your computer restarts, start any Office 2008 for Mac program.
    Note The Office Setup Assistant runs.
  11. Accept the software license agreement, and then provide your valid product key.
    Note The product key is located on the back of the Office 2008 for Mac DVD sleeve or on the back of the Installation Guide.

Method 2: Remove Receipts

To remove receipts, follow these steps:
  1. On the Go menu, click Computer.
  2. Double-click your hard disk icon. The default name will be Macintosh HD.
  3. Open Library, and then open Receipts.
  4. Drag all files that begin with "Office2008_en" to the Trash.
Note These files are not always found on the computer.

If you have Mac OS X Snow Leopard (10.6) or Lion (10.7), continue with these steps:
  1. On the Go menu, click Go to Folder.
  2. Type this text in the Go to folder box, and then click Go:

  3. Arrange files and folders in alphabetical order.
  4. Drag all files that begin with "com.microsoft.office" to the Trash.

Method 3: Restart the computer in safe mode

For information about how to enter safe mode in Mac OS, see the following Microsoft knowledge base article:

2398596 Perform a clean startup (safe boot) to determine whether background programs are interfering with Office for Mac

Method 4: Create a new Mac user

For information about how to create a new user account, see the following Microsoft knowledge base article:

2439218 Testing your user account to troubleshoot Office for Mac applications
For steps and instructions on how to obtain a new product key, click the following article number to view the article in the Microsoft Knowledge Base:

2279109 Obtain a new product key for Office for Mac

Article ID: 969064 - Last Review: Sep 13, 2011 - Revision: 1