How to manually download the latest definition updates for Microsoft Security Essentials

follow these steps:

1. Download the Microsoft Security Essentials virus and spyware definition update file that is appropriate for your version of Windows:
   • To download the file for a 32-bit (x86-based) version of Windows, click the following link:
     http://go.microsoft.com/fwlink/?LinkID=87342
   • o download the file for a 64-bit version of Windows, click the following link:
     http://go.microsoft.com/fwlink/?LinkID=87341 
   Note You must be running a 64-bit version of Windows to run a 64-bit version of Microsoft Security Essentials. 64-bit versions of Windows include x64-based versions of Windows.
2. 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.
3. To install the saved file, follow these steps:
   • On Windows XP:
     
     Double-click the file, and then click OK.
   • On Windows Vista or on 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.
4. 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 have been updated. To do this, open Microsoft Security Essentials, click Update, and then examine the virus and spyware definitions status.