I have been using Microsoft Security Essentials (MSE) from when it was in Beta. I really like it as it is very quite and most does catch any virus that try to creep in via USB sticks or from PDF files (which the ones I mostly come across)
The only sticky point is that the Virus Definition Updates happen automatically via Windows Updates. Since my laptop is online only at certain periods of the day, I saw that my virus updates were delayed for multiple days.
So I decided to schedule a manual update of the definition files during a specifc time of the day when I would most probably be online at home (I set it up to run at around 8am everyday, at which time my laptop is most probably on and online as I do my morning email checks)
The command to do the virus update is simple:
"%ProgramFiles%\Microsoft Security Essentials\MpCmdRun.exe" -SignatureUpdate
The way to automate this is to use the Scheduled Tasks (at command) inbuilt into Windows.
2. I recommend that you create a folder and put all of your tasks inside that so that it is easier to track
6. Now setup a new trigger to run it whenever you want the updates to run
Sit Back and enjoy your virus definition Updates.. :)