Safe Mode in Windows loads the operating system in a limited state, which can be helpful for troubleshooting and correcting PC issues. Many of the standard services and features of the Windows operating system are not available in safe mode, including the Windows Installer Service.
It is not possible to uninstall software in Safe Mode if the service is not running, that is highly problematic if a software is responsible for PC issues and if it cannot be removed on your system when it is running in normal mode.
There is however an option to start the Windows Installer Service in Safe Mode, so that software can be uninstalled afterwards.
The Windows Installer Service can't be started immediately, it is necessary to patch the Registry first. If you try to uninstall a program in Safe Mode, you get the following error message pointing at the cause of the issue:
The Windows Installer Service could not be accessed. This can occur if the Windows Installer is not correctly installed. Contact your support personnel for assistance.
Fixing the issue
Open the Windows Registry Editor in the following way:
It can also be launched by clicking on the start orb, and entering regedit in the run box in the Start Menu followed by enter on Windows 7 and earlier Windows systems.
Locate the following Registry key
Right-click on Minimal and select New > Key. Name the key MSIServer and change the default value to Service by double-clicking it.
Side note: I tested this under windows 8 recently, and here you did not have to rename the value to Service anymore. This may now also be the case on other editions and versions of Windows, but has not been tested by me.
This makes the Windows Installer Service available in minimal Safe Mode. You may want to repeat the steps for the networking Safe Mode as well. All steps are the same, except for the starting Registry key.
The Windows Installer Service needs to be started afterwards, this can be done by clicking on the start orb again, entering services.msc and hitting enter.
On Windows 8, you tap on the Windows key, type services.msc, and select the appropriate result from the list.
Locate Windows Installer in the services listing, right-click it and select start. Alternatively execute the following command via the command line:
net start msiserver
It is furthermore possible to issue all commands via the command line. To enable Windows Installer in minimal Safe Mode execute the following command:
REG ADD "HKLM\SYSTEM\CurrentControlSet\Control\SafeBoot\Minimal\MSIServer" /VE /T REG_SZ /F /D "Service"
For Safe Mode with network:
REG ADD "HKLM\SYSTEM\CurrentControlSet\Control\SafeBoot\Network\MSIServer" /VE /T REG_SZ /F /D "Service"
The freeware SafeMSI offers to automate the Registry editing and service starting. Just double-click the program in Safe Mode to enable Windows Installer.
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