Note You must be running a 64-bit version of Windows to run a 64-bit version of Microsoft Security Essentials. The 64-bit versions of Windows include x64-based versions of Windows.
Click Run to install the definition update file immediately. Or, click Save to save the file to the computer. If you click Save, remember the folder where you saved the file.
To install the saved file, follow these steps:
Windows XP Double-click the file, and then click OK.
Windows Vista or Windows 7 Right-click the file, and then click Run As Administrator. If you are prompted for an administrator password or for confirmation, type the password, or click Continue.
When the definition update file runs, a file extraction dialog box appears. The dialog box indicates that the definition update is installing. After the file extraction dialog box closes, you can verify that the virus and spyware definitions were updated. To do this, open Microsoft Security Essentials, click Update, and then examine the virus and spyware definitions status.
How to troubleshoot update issues for Microsoft Security Essentials
To resolve an issue in which Microsoft Security Essentials does not update automatically, go to the following Microsoft website: