Fix: A Fatal Error Occurred during Installation

Users experience the error message “Error 1603: A fatal error occurred during installation” when they are either installing a new program or they are updating a program to a newer version.

This error usually occurs when you are already trying to install an application which is already installed. Or the folder where you are trying to install is encrypted or the SYSTEM doesn’t have enough permissions in the drive/folder. To resolve this error, there are several workarounds. This is a very common error and hopefully will be fixed if you follow the instructions listed below.

Solution 1: Running Microsoft Fixit

Microsoft has released an official program which targets installation problems on the computer. It fixes registry keys in 64-bit architectures and also fixes the registry keys which control the update data. According to the official documentation, it fixes problems which don’t let you install or uninstall programs.

  1. Navigate to the official Microsoft website and download the Fixit application.

  1. After downloading the program, run the troubleshooter. Press Next. Now the program will automatically start searching for any corrupted registry keys and other problems that might be present.

  1. A few moments after running the troubleshooter, you will be given an option whether the problems occur either while installing or uninstalling. Select the correct option according to your case and proceed.

  1. After the troubleshooting is complete, restart your computer and try installing or uninstalling the program again.

Solution 2: Giving Full Permission to Drive

The error message under discussion might also arise if the drive you are trying to install doesn’t grant enough permission to the user SYSTEM to continue with the installation. The user group SYSTEM is responsible for installing or uninstalling various programs and applications. We will grant the required permissions and see if this fixes the problem.

  1. Open “This PC”. Locate the hard drive you are trying to install the program into. Right-click it and select “Properties”.
  2. Now navigate to the “Security” tab and click Edit in front of permissions.

  1. Make sure that the user group SYSTEM has complete permissions. After granting all the permissions, click Apply. The computer might take several minutes to implement the changes on all the files present inside the drive. The time may vary according to the number of files you have.

  1. Navigate to the previous window again and click Advanced.

  1. Once the new Window pops up, click Change permissions.

  1. Select Administrators from the list and select the option This folder, subfolders, and files in front of Applies to. Now grant all permissions. Press OK to save changes.

  1. Do the same steps for the user group SYSTEM. After implementing all the changes, press Apply and exit. Now check if the problem at hand got solved.

Solution 3: Checking Windows Update

Another problem which arose after the newer updates of Windows 10 in early 2018 was with the Windows Update module. Programs such as Python etc. were reported to cause problems whenever the computer was installing updates or downloading them.

The only workarounds which were reported to work for this issue were to either Disable Windows Update or wait for it to finish. It seems that Windows update also uses Windows installer to implement all the updates on your computer. If the installer is not free, you will be forced to the error message under discussion.

Solution 4: Restarting Windows Installer Service

If all the above methods don’t work out, you can try restarting the Windows Installer Service. Windows Installer is an API and software component of Microsoft Windows which is used for installation, maintenance, and removal of software from your computer. They are used by several applications to install their packages on your Windows. Re-registering the installer might solve the problem for us.

  1. Press Windows + R and type “services.msc” in the dialogue box to launch the services tab.
  2. Once in services, locate the entry “Windows Installer”. Right-click it and select “Properties”.

  1. The service will most probably be stopped. Click on the “Start” button and press OK to save changes.

  1. Press Windows + R and type “msiexec /unregister” in the dialogue box and press Enter. This will unregister the installer.

  1. Now press Windows + R again and type “msiexec /regserver” and press Enter.
  2. Now check if the problem got solved. Consider doing a restart and try again if it didn’t.

If even re-registering the installer service doesn’t work, we will execute more intense commands in the command prompt before moving on to the tips.

  1. Press Windows + S, type “command prompt”, right-click on the application and select “Run as administrator”.
  2. Once in command prompt, execute the following commands one by one:

%windir%\system32\msiexec.exe /unregister

%windir%\syswow64\msiexec.exe /unregister

%windir%\system32\msiexec.exe /regserver

%windir%\syswow64\msiexec.exe /regserver

  1. Restart your computer. After power cycling, press Windows + R, type “regedit” in the dialogue box and press Enter.
  2. Now navigate to the following address:


  1. Find the key “msiserver”. Click on “DisplayName” at the right-navigation pane and change the value to “C:\WINDOWS\SysWOW64\msiexec.exe /V”.

  1. Now open an elevated command prompt again and type the command “C:\WINDOWS\SysWOW64\msiexec.exe /regserver” and press Enter.
  2. Restart your computer and check if this made any difference.


  • Consider closing all the background processes and try installing the program again.
  • Check if the software or any older version of it is already installed (Windows + R and “appwiz.cpl”). If there is, you have uninstall it before you can install a newer version.
  • Make sure that the space requirements are being fulfilled. Consider making extra space on your drive.
  • You can also remove temporary files from your drive and see if this makes any difference.
  • Since this problem can occur with any software, we cannot go through their fixes in one article. Check out our other articles which target each software one by one.
  • If this problem is happening with the majority of the programs, you should backup your data and do a fresh installation of Windows.
  • You can also perform a repair of the currently installed operating system.

Kevin Arrows

Kevin Arrows is a highly experienced and knowledgeable technology specialist with over a decade of industry experience. He holds a Microsoft Certified Technology Specialist (MCTS) certification and has a deep passion for staying up-to-date on the latest tech developments. Kevin has written extensively on a wide range of tech-related topics, showcasing his expertise and knowledge in areas such as software development, cybersecurity, and cloud computing. His contributions to the tech field have been widely recognized and respected by his peers, and he is highly regarded for his ability to explain complex technical concepts in a clear and concise manner.