Solved: The Windows Installer Service Could Not Be Accessed

The Windows Installer Not Working Windows 10

"I recently upgraded to Windows 10 from Windows 8. Now, every time I try to download a new program, it keeps telling me I have to wait until other program finishes installing. The same thing happens when I try to uninstall a program. I have no clue how to fix this, and it is really hindering me. I can't install anything! Please help me. Thanks!"

How to Fix the Windows Installer Service Could Not Be Accessed Error 

You may see an error message popping up, telling you The Windows Installer Service could not be accessed when you try to install a software. At this time you cannot continue your installation. Here are some methods that can help you get rid of this error.

Method One. Uninstall the earlier version of the software you want to install

If the Windows installer not working, you can remove the earlier version of the software you want to install before you install the new one. Installing a software without removing the older version can sometimes cause unexpected issues.

Method Two. Confirm the installer service is running

• At the start, search for Run.
• In the Open box, type msconfig, and then click OK. 
• On the Services tab, click to select the checkbox that is next to Windows Installer.
• Click OK, and then click Restart to restart the computer. 

Method Three. Re-register Microsoft installer service

If you find the Windows installer service isn't running, you can Re-register the installer service. Re-registering Microsoft Installer Service is another good method to solve the Windows Installer Service could not be accessed error.

1. Press Win + R keys. Type “cmd” and hit Enter.
2. In Command Prompt, type the following lines. You need to hit Enter every time after each line.

   %windir%\system32\msiexec.exe /unregister
   %windir%\system32\msiexec.exe /regserver
   %windir%\syswow64\msiexec.exe /unregister
   %windir%\syswow64\msiexec.exe /regserver
3. Close Command Prompt and restart your computer.
4. You have re-registered Windows Installer Service. Check and see if you fix the Service could not be accessed error.

Method Four. Reinstall Windows installer

If all the methods above all fail to help you, the last choice is to reinstall the Windows installer. 

1. At the start, search for CMD.
2. At the command prompt, type the following lines. Press ENTER after you type each line.
   cd %windir%\system32
   ren msi.dll msi.old
   ren msiexec.exe msiexec.old
   ren msihnd.dll msihnd.old
3. At the command prompt, type exit, and then press ENTER.
4. Restart your computer.
5. Update the Windows Installer files to the latest version. To do so, visit the Microsoft Web sites, and then download and install Windows Installer.
6. After the installation of the Windows Installer is complete, shut down and restart your computer normally before you install programs.

Extra Tip: Recover data after you have fixed the error

Any of the methods above may cause data loss, if you have data loss problem after you have fixed the Windows installer service error, we can help.
EaseUS Data Recovery Wizard can help fix this problem. It’s fully compatible with Windows 10/8.1/8/7 and former Windows versions. You can free download it and follow the steps to restore lost data from Windows 10/8/7 now.

1. Launch EaseUS Data Recovery Wizard Select a location(where the recycle bin is) and click "Scan".

2. The software will start a quick scan first. After the quick scan completes, a deep scan will automatically launch in order to find more files.

3. Choose the file(s) you want to recover by file types from the scanning results. Click "Recover" button to recover the selected files. You'd better choose a different location instead of the original hard drive to avoid data overwriting.