It is best to uninstall Microsoft Security Essentials (MSE) from the Windows Control Panel via Add/Remove Programs (XP) or Programs and Features (Vista and Windows 7). However, sometimes the uninstallation process fails to complete.
Even worse, the entry for MSE may also disappear from the list of installed programs – so you can’t try to uninstall it again in the usual way. Until MSE is completely removed you will likely be unable to install any antivirus program – and you shouldn’t even try because having two (or one and a half!) antivirus programs running at the same time can cause more serious problems such as Windows freezing or not starting up.
If you have not been able to uninstall MSE in the usual way, you will need to forcibly remove it – create a new system restore point first.
How To Forcibly Uninstall MSE – There are 2 main methods to try – the first method may work but it depends how corrupted your MSE installation has become.
Note: If you can only start up in Safe Mode (e.g. normal Windows login freezes/crashes due to having more than 1 antivirus program installed) this method will not work – skip to Method 2 below.
1. Download a new MSE installation file from the Microsoft download page here.
2. Save the installation file (mseinstall.exe) to the Desktop.
3. Press the Windows Key and the R key at the same time to open the Run window.
4. Drag and drop the MSEinstall.exe installation file you downloaded into the Run window.
5. The Run window entry should now display the following (assuming that Windows is installed on C: partition – it usually is):
In XP – C:\Documents and Settings\[your username]\Desktop\mseinstall.exe
In Vista/7 – C:\Users\[your username]\Desktop\mseinstall.exe
6. Add a single space after this text then type /U so the Run window should now contain:
In XP – C:\Documents and Settings\[your username]\Desktop\mseinstall.exe /U
In Vista/7 – C:\Users\[your username]\Desktop\mseinstall.exe /U
7. Press the OK button to begin uninstallation of MSE – if the process completes successfully, shut down and restart your computer – MSE should be gone and you can install a new antivirus program.
If the uninstallation process failed, move on to Method 2 below.
1. Go to the Microsoft support page for MSE version 2 here.
Note: MSE version 2 was released more than a year ago (Dec 2010) so it is almost certainly the version you have installed – if you still have version 1, go to the Microsoft support page for MSE version 1 here instead.
2. Scroll half way down the page and click on the Microsoft Fixit button to ‘Fix it for me’ automatically.
3. If using Internet Explorer click ‘Run’ in the File Download dialog box or, in other browsers, save the Fixit file to the desktop then run it.
4. Once the Fixit program runs, just follow the guided steps to complete uninstallation of MSE.
5. If the process completes successfully, shut down and restart your computer – MSE should be gone and you can install a new antivirus program.
Note: If the Fixit program stalls for a long time (i.e. the progress bar stops before reaching the end) it may have only removed part of MSE and needs to be run again to finish – close the Fixit program then shut down and restart your computer and run the Fixit again – this time it should progress to completion and remove the rest of MSE.
To do their job, antivirus programs are deeply embedded into Windows which can sometimes cause problems trying to uninstall them. This guide on how to uninstall MSE should succeed when normal uninstallation fails.
After successful removal of MSE, check in Windows Security Center (accessed from Control Panel) that the correct antivirus program is now listed e.g. ‘none’ if you have no antivirus installed.
Security Center sometimes gets confused and still lists an old antivirus program – which could prevent you installing a new one. To resolve this problem, see my guide on fixing the wrong antivirus listed in security center.