Office 2008 for Mac error: "Microsoft Office 2008 cannot start because it is already in use"

When you try to start any Microsoft Office 2008 for Mac program, you receive an error message that resembles the following:

This issue can occur when the following conditions are true:

• You install Microsoft Office 2008 for Mac on multiple computers.
• You install the product by using the same product key from the previous Microsoft Office 2008 for Mac installations.

These are example scenarios when this may occur:

• You install Office 2008 for Mac Home and Student Edition on multiple computers by using the same product key.
  
  Note Because this version of Office for Mac includes three separate product keys, in this scenario, you should use a different product key for each installation.
  
• You are connected on a large network, such as a school network. Somebody on that network is using the same product key.
  
  Note Because you may have been provided a product key that another user is using, in this scenario, you should contact the school administrator or IT department to obtain a new product key.
  

When you start an Office 2008 for Mac program, the program sends out a request over the network. The request looks for other Office 2008 for Mac programs that are running on other computers that are connected to the network. If other Office 2008 for Mac programs are running, the programs compare product ID numbers to the requesting program. If any of those product ID numbers match, the requesting program does not start. Additionally, the warning message that is mentioned in the "Symptoms" section appears.

Note This issue does not occur with Office for Mac 2011. You can download the Office for Mac 2011 trial version and try it for 30 days for free, or you can purchase Office for Mac 2011.

To download the trial version, visit the following Microsoft website: To buy Office for Mac 2011, visit the following Microsoft website:

Some licenses enable you to install and activate only one copy of Office for Mac 2008 on one computer. But some licenses allow for more installations. To verify the number of installations that your license allows for, refer to the following table:

If your license lets you install and activate only one copy of Office for Mac 2008 on one computer, you must purchase another copy of the product if you want to install it on more than one computer. You also have the option to purchase Office for Mac 2011 for your other computer.

To buy Office for Mac 2011, visit the following Microsoft website:If your license lets you install and activate Office for Mac on multiple computers, you must verify that the same product ID is not used on more than one computer. To do this, follow these steps.

Step 1: Disconnect from the Internet or from the network

Follow the steps that are appropriate for the network connection method that you are using.

AirPort connection

1. On the Apple menu, click System Preferences.
2. In the Internet & Wireless section of System Preferences, click Network.
3. Highlight AirPort in the left bar. If the Status is On, click the Turn AirPort Off button.
4. Close the Network window. Go to the "Step 2: Compare your product ID number" section.

Ethernet connection

1. On the Apple menu, click System Preferences.
2. In the Internet & Wireless section of System Preferences, click Network.
3. Note the Ethernet settings for your network connection. This information includes the IP Address, the Subnet Mask, the Router, and so on.
4. Close the Network window.
5. On the Apple menu, click Shut Down.
6. Unplug the Ethernet cable from the Ethernet port on the back of your computer. Then, restart the computer.
7. Go to the "Step 2: Compare your product ID number" section.

Step 2: Compare your product ID number

1. Start one of the Office applications, such as Microsoft Word or Microsoft Excel. The following steps assume that you start Word.
2. Click Word, and then click About Word.
3. The product ID is listed at the bottom of the window. It is displayed in the following format:
   XXXXX-XXX-XXXXXXX-XXXXX.
   Note the first 15 numbers of the product ID.
4. Repeat steps 1 through 3 on another computer that is running Office for Mac 2008.
5. Compare the two sets of Product IDs.

Product IDs are different

If the Product IDs are different on two or more computers, but you still receive the error message that is mentioned in the "Symptoms" section, follow these steps:

1. Disconnect from the Internet.
2. Uninstall Office 2008 for Mac.
3. Reinstall Office 2008 for Mac.

For more information about how to uninstall and reinstall Office for Mac, click the following article number to view the article in the Microsoft Knowledge Base:Product IDs are the same

If the Product IDs are the same, and your license enables you to install and activate Office for Mac on multiple computers, you must remove the licensing information from one of the computers. Then, enter one of the other product keys that were included with the Microsoft Office 2008 for Mac package. To remove the licensing information, follow these steps:

1. On the Go menu, click Applications.
2. Open the Microsoft Office 2008 folder, and then open the Office folder.
3. Drag OfficePID.plist to the Trash.
4. Close all windows.
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. pen the Preferences folder, and then open the Microsoft folder.
8. Drag the Office 2008 folder to the Trash.
9. Restart Office 2008, and then enter a new or unused CD-Key when you are prompted.

For more information about how to change licensing information from one computer to another, click the following article number to view the article in the Microsoft Knowledge Base :

Microsoft Office for Mac Standard, Microsoft Office for Mac Business, and Microsoft Office for Mac Media Edition are licensed for use on up to two personal computers (one portable and one desktop computer) by a single user. Microsoft Office for Mac Home and Student Edition is licensed for use on up to three personal computers in the same household.