Fix: Only one instance of wusa.exe is allowed to run

This type of Windows update error is mostly associated with the older versions of the Windows operating system and it’s the most common on the Windows 7 OS. Performing updates on older versions of the Windows OS was definitely more difficult than it is now and there was always a risk of receiving random error codes.

The “Only one instance of wusa.exe is allowed to run” error can be fixed in a variety of different ways and it occurs in various different scenarios such as updating Internet Explorer, installing a standalone update manually, etc. That is why it’s important to keep track of all methods and try them out as soon as possible.

Solution 1: Disable Your Third-Party Antivirus

Third-party security tools can pretty much spoil all the fun and cause all types of errors on users’ computers. These errors are not so common but, when they appear, the real cause is very difficult to locate yet easy to solve.

You will need to disable or uninstall the third-party antivirus tools before initiating the process which throws the error. The error occurs mostly with McAfee users to the instructions are for them. Steps are quite similar from antivirus to another.

1. Open your McAfee antivirus user interface by double-clicking on its icon on the Desktop or by double-clicking on its icon in the bottom right part of your taskbar.
2. From its home page, click on the Real-Time Scanning under Virus and Spyware protection which will open a new window.

3. Under the Real-Time Scanning: On screen on top of the window, click on Turn off and choose the amount of time you need at maximum before you click Turn off.
4. Check to see if the error still appears.

Solution 2: Check Task Manager for Another Instance of “wusa.exe”

As the name of the error code is quite self-explanatory, a possible fix would be to check whether there is a second instance of wusa.exe running and preventing your from proceeding with the desired update. This method is not always successful but it’s very easy to check it out.

1. Use the Ctrl + Shift + Esc key combination in order to bring up the Task Manager. Alternatively, you can use the Ctrl + Alt + Del key combination and select Task Manager from the menu. You can also search for it in the Start menu.

2. Click on More details in order to expand the task manager and search for the wusa.exe entry displayed on the list in the Processes tab of Task Manager. If you see multiple entries, right-click on them and choose the End task option from the context menu which appears.
3. Click Yes to the message which is going to be displayed: “WARNING: Terminating a process can cause undesired results including loss of data and system instability….”

4. Restart your computer and check to see if you are able to proceed without receiving the same error now.

Solution 3: Check the Status of the Windows Installer Service

If there is something wrong with the Windows Installer Service, it’s natural to expect that any problems with it are going to affect any possible installation or update. Luckily, it’s quite easy to restart or repair a service and this is what makes this method highly successful among users.

1. Open the Run dialog box by using the Windows Key + R key combination. Type “services.msc” without the quotation marks in the Run dialog box and click OK.

2. Locate the Windows Innstaller Service, right-click on them and select Properties.
3. Make sure that the option under Startup type in Windows Store Services’ Properties is set to Automatic.
4. If the service is stopped (you can check that just next to the Service status message), you can start it immediately by clicking on the Start button.

You may receive the following error message when you click on Start:

 “Windows could not start the Windows Installed Service on Local Computer. Error 1079: The account specified for this service differs from the account specified for other services running in the same process.”

If this occurs, follow the instructions below to fix it.

1. Follow the steps 1-3 from the instructions above in order to open Windows Update Service properties.
2. Navigate to the Log On tab and click on the Browser… button.

3. Under the “Enter the object name to select” box, type in your computer’s name and click on Check Names and wait for the name to become authenticated.
4. Click OK when you are done and type in the administrator password in the Password box when you are prompted with it.

Note: Another useful thing you can perform with the Windows Installer Service is to reregister it and check to see if that solved the problem. This will also take a minute and it can actually solve the problem.

1. Click the Start menu and type in the following command in it before pressing Enter in order to run it:

%windir%\system32\msiexec /unregserver

2. Now you only need to repeat the same process only this time with the command below:

%windir%\system32\msiexec /regserver

3. Make sure you provide any administrator permissions if prompted to do so. Check to see if the problem with wula.exe still appears.

Solution 4: Install the Update Manually

Unfortunately, it seems that sometimes the only way to actually solve this problem is to take matters into your own hands and install the update manually if the automatic process is simply not working for you. Good luck! The process of installing is somewhat more complicated but it’s nothing too difficult and you will end up with a fully updated PC.

1. Navigate to this page and locate the latest Servicing Stack Update for your version of Windows 7. The current version will be displayed in bold. Make sure you install the updates from top to bottom and be patient for them to finish.

2. These updates are a must if you want to avoid the endless search for new updates on your computer as these updates contain the upgraded version of the Update Agent which means you won’t struggle with the future updates.
3. Download the files to your computer, close all programs, run the files, and follow the instructions on screen in order to complete the update. Check to see if the search for updates is successful and whether the “wusa.exe” error still appears.