Those of you with Microsoft’s new-ish anti-virus program, Security Essentials, will probably know that it updates itself according to your Windows Update settings.  For most people, this is fine as it will be set to automatic daily updates; but for those with other settings, this could cause problems.

Update: I have updated and re-posted this post to cater for file path changes in the recently released version 2 of MSE. Also, since the reloaction of the site, I've had to remove the screenshot as I went and lost the images *facepalm*

MSE comes with a command line application, MpCmdRun.exe, located in the installation folder (C:\Program Files\Microsoft Security Client\Antimalware default).  Running this program with the -SignatureUpdate argument will update MSE to the latest virus definitions.  “Scheduled task” comes to mind!

If you’re new to scheduled tasks in Windows then you’ll find them very useful from now on!  If you’re already using them then you’ve probably gone to make a task already.  Either way, here’s how to set up a schedule to update MSE every 3 hours (in Windows 7 – may differ in older versions).

1. Click the Start orb, type “task scheduler”, then click on Task Scheduler in the search results.
2. In the left pane, click on Task Scheduler Library.
3. In the right pane, click Create Task…
4. Give the task a name and description to suit its purpose.  Change the user account to System (this runs the task as the System account, which means, among other things, it won’t pop-up in a command prompt on your account while you work).  To change the user account, click Change User or Group.  Type System in the text area and click OK.  Tick the box that says “Run with highest privileges”.
5. Now move to the Triggers tab.  Click New.  From the drop-down menu at the top, select “At startup”.  You can choose to delay the task if you wish, but the important part is “Repeat task every” – choose or type a value in here (e.g., 3 hours) and make sure the checkbox is ticked.  Set the duration to “indefinitely” – this will run the task until you shut down the computer.  Click OK to add the trigger.
6. Move to the Actions tab.  Click New.  The action is to start a program, so leave the drop-down menu as it is (assuming it’s on “Start a program”).  In the Program/script textbox, either browser to MpCmdRun.exe or type in the path:
   "%ProgramFiles%\Microsoft Security Client\AntiMalware\MpCmdRun.exe".
   In the “Add arguments” textbox, type “-SignatureUpdate”.
7. For the Conditions and Settings tabs, those options are pretty much all down to your personal preference, so go through those to your liking.
8. Click OK when you’re all done, and that should be it!  Keep an eye out for the updating MSE icon in the system tray the next time your task is triggered.

Hope that helps!  Any questions, post them as a comment and I’ll see what I can do :)