When you try to install an update for Microsoft Office for Mac 2008 or 2011, you receive the following error message: 

CAUSE

To resolve this problem, follow the steps provided in each Method. 

Method 1: Disconnect the external hard disk drive

Disconnect any external hard disk drives that you may have connected to your Mac then try to apply the update. 

If you do not have an external hard disk drive or this step did not resolve the issue, go to "Method 2: Quit all Applications." 

Method 2: Quit all Applications

To quit active applications, including Time Machine, follow these steps:

1. On the Apple menu, click Force Quit.
2. Select an application in the "Force Quit Applications" window.
   Note You cannot quit Finder.
   
   
3. Click Force Quit.
   
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4. Repeat the previous steps until you quit all active applications.

Warning When an application is force quit, any unsaved changes to open documents are not saved.

If the issue continues to occur, go to "Method 3: Check if the update is already installed." 

Method 3: Check if the update is already installed 

The error message indicates that you already have the update and you do not have to apply it again. Make sure that the update that you are trying to apply is not already installed. To do this, follow these steps:

1. Open one of the Office for Mac applications such as Word.
2. On the Word menu, click About Word.
3. Note the version of the software. The version number will be displayed underneath the application title. Click OK to quit the window.
4. On the Help menu, click Check for Updates, and then click Check for Updates again.
5. Note the version of the update.

If the software version in the "About Word" window is greater than the update version, the update has already been installed and no additional action is required. However, if the update version is greater than the software version, the update has not been installed. Continue following the steps in the article.

Method 4: Check if Microsoft Office 2008 or 2011 is in Applications

If the Microsoft Office folder is not in Applications, Microsoft AutoUpdate will not detect Office on the Mac and will be unable to install updates. To verify that the Microsoft Office folder is in the correct location, follow these steps:

1. On the Go menu, click Applications.
2. Look for Microsoft Office 2008 or Microsoft Office 2011.

If one of these folders is in Applications, go to "Method 5: Remove and reinstall Office for Mac."

If Microsoft Office 2008 or Microsoft Office 2011 is not in Applications, you will have to locate the folder and move it to Applications. To do this, follow these steps:

1. Quit all running applications.
2. On the File menu, click Find.
3. In the search parameters, leave the boxes set to "Kind" and "Any."
4. In the search window, type Office 2008 or Office 2011, and then press Enter.
5. Locate Microsoft Office 2008 or Microsoft Office 2011 in the search results, and then drag the folder to your desktop.
6. On the Go menu, click Applications.
7. Drag Microsoft Office 2008 or Microsoft Office 2011 from your desktop to Applications.

Try downloading and installing the update. If the issue continues to occur, go to "Method 5: Remove and reinstall Office for Mac."

Method 5: Remove and reinstall Office for Mac

Important We recommend that you find your Office 2008 for Mac or Office for Mac 2011 installation media and product key before you follow the steps in Method 5 and 6. If you have an upgrade version of the Office 2008 software, make sure that you have previous versions of Office for Mac to complete a reinstall.

Warning Any custom preferences will be set back to default. Also, any custom dictionaries or auto correct settings restore to default.


To remove and reinstall Office 2008 for Mac:

1. Quit all running applications.
2. On the Go menu, click Applications.
3. Drag Microsoft Office 2008 to the Trash.
4. On the Go menu, click Home.
5. 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.
   
   
6. Open Preferences.
7. Open Microsoft, and then Office 2008.
8. Drag Microsoft Office 2008 settings.plist to the Trash.
9. On the Apple menu, click Restart.
10. Reinstall Office 2008 for Mac.

To remove and reinstall Office for Mac 2011:

1. Quit all running applications.
2. On the Go menu, click Applications.
3. Drag Microsoft Office 2011 to the Trash.
4. On the Go menu, click Home.
5. 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.
   
   
6. Open Preferences, and then drag the Microsoft folder to the Trash.
7. On the Apple menu, click Restart.
8. Reinstall Office for Mac 2011.

If the issue continues to occur, go to "Method 6: Completely remove and reinstall Office for Mac."

Method 6: Completely remove and reinstall Office for Mac

You must manually remove all files for Office for Mac on your computer. For information about how to remove Office for Mac from your computer, follow the steps in one of the following Microsoft knowledge base articles:

For Office 2008 for Mac:
2500821 (http://kbalertz.com/Feedback.aspx?kbNumber=2500821) How to manually remove Office 2008 for Mac


For Office for Mac 2011:
2398768 (http://kbalertz.com/Feedback.aspx?kbNumber=2398768) How to completely remove Office for Mac 2011

After you remove Office for Mac, reinstall it. 

The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.