Step 1: Restart your computer
Step 2: Make sure the “Microsoft Security Essentials” service is set to automatic and is started
- In Windows Vista and Windows 7, click Start, click in the Start Search box, type services.msc, and then press Enter.
- Search for Microsoft Antimalware Service. Right-click it and select Properties or double-click it to open the service.
- Check to make sure that the "Startup Type" is set to "Automatic."
- Click the Start button to start the service. If the Start button isn't available, click the Stop button, and then click the Start button to restart the service.
- Make sure you note any errors that may appear during this process, submit a case online, and include the error information.
Step 3: Remove any existing Internet security programs
- In Windows Vista or Windows 7, click Start, click in the Start Search box, type appwiz.cpl, and then press Enter.
- In the list of installed programs, uninstall any third-party Internet security programs.*
- Restart your computer, and then try to install Microsoft Security Essentials again.
*Some Internet security apps don't uninstall completely. You may need to download and run a cleanup utility for your previous security app in order for it to be completely removed.
When you remove Internet security programs, your computer is unprotected.
Step 4: Uninstall/reinstall Microsoft Security Essentials
- In Windows Vista and Windows 7, click Start, and in the Start Search box, type appwiz.cpl, and then press Enter.
- In the list of installed programs, click Microsoft Security Essentials, and then uninstall it.
- If prompted, restart your computer, and then try to install Microsoft Security Essentials again.