If you use a laptop, or you tend to shut down your computer when it’s not in use, then you’ve probably missed out on at least a few virus definitions updates from Microsoft Security Essentials (MSE). The problem lies in that MSE is designed only to update once every 24 hours, and if your computer is not powered on or is not connected to the internet at the time, it will just pass by. But, we can fix all of that by setting up a simple task rule in Windows; this works similar to the tutorial for fixing the Java update program.
Step 1: Open Task Scheduler
In the Start Menu, Search for task scheduler and Press Enter.

Step 2: Create Task
In the right-pane of the Task Scheduler Click Create Task…
Do not confuse this step, Create Basic Task will not work the same.

Step 3: The General Tab
Name your task something relevant and give it a description. Now we need to change the user to SYSTEM, to do this Click Change User or Group… and then in the object name box Type system and Click OK. Once that is done, you can change the configuration to Windows 7 or whatever version of Windows you are using.

Step 4: Triggers
Click the Triggers tab and from there Click New… The edit Trigger window should appear. You want to Begin the task on a schedule, set to Daily and Recur every one day.
Once you have that go down to the Advanced settings are and set Repeat task every to 6 hours; to set this you’ll have to manually Type in 6 hours as the drop-menu doesn’t show it. Now set the duration to Indefinitely. Make sure Enabled is checked and then Click OK.

Step 5: Actions
Click the Actions tab and from there Click New… Here you want to Type –SignatureUpdate into the arguments box, and then Click Browse.

Step 5: Actions, file location
Browse to the executable MpCmdRun.exe, this is typically located at:
C:\Program Files\Microsoft Security\MpCmdRun.exe |

Step 6: Conditions
Click the Conditions tab and Check the box under Network. For the network connection name use Any connection. This will save your PC the trouble of disregarding the task if an internet connection is not available and makes sense because you cannot update MSE without the internet.

At this point, the only thing left to do is Click OK to save the task.
Done!
Your new schedule for Microsoft Security Essentials is setup, and you shouldn’t have any more problems with missing out on virus definition updates.