How to Fix the “Windows Installer Service Could Not Be Accessed” Error in Windows XP

If you encounter the “Windows Installer Service Could Not Be Accessed” error while trying to install a program on your Windows XP machine, don’t panic. This error can occur for several reasons, such as the Windows Installer service not running, incorrect registry settings, or a conflict with other software. Fortunately, there are several methods you can try to resolve this issue.

Method 1: Unregister and Re-register the Windows Installer

One of the most effective ways to fix the “Windows Installer Service Could Not Be Accessed” error is to unregister and re-register the Windows Installer. Here’s how to do it:

1. Click Start, then click Run.
2. Type MSIEXEC /UNREGISTER and then click OK. Even if you do this correctly, it may look like nothing occurs.
3. Click Start, then click Run.
4. Type MSIEXEC /REGSERVER and then click OK.
5. Try your Windows Installer-based application again.

If the issue persists, move on to the next method.

Method 2: Start the Windows Installer Service

Another common cause of the “Windows Installer Service Could Not Be Accessed” error is that the Windows Installer service is not running. To start the service:

1. Click Start, then click Run.
2. Type services.msc and click OK.
3. In the Services window, locate the Windows Installer service.
4. Right-click the service and select Properties.
5. In the Startup type dropdown, select Automatic.
6. Click Start to start the service.
7. Click OK to close the Properties window.
8. Try your Windows Installer-based application again.

If the service is already running, try restarting it.

Method 3: Check and Modify Registry Permissions

Incorrect registry permissions can also cause the “Windows Installer Service Could Not Be Accessed” error. To check and modify registry permissions:

1. Click Start, then click Run.
2. Type regedit and click OK.
3. Navigate to the following key: HKEY_CLASSES_ROOT.
4. Right-click the key and select Permissions.
5. Ensure that the SYSTEM account has Full Control permissions.
6. If the SYSTEM account is not listed, click Add, enter SYSTEM, and click OK.
7. Select the SYSTEM account, check the Full Control box under Allow, and click OK.
8. Close the Registry Editor and try your Windows Installer-based application again.

If none of the above methods work, you may need to repair your Windows XP installation or seek further assistance from Microsoft Support.