Step 1: Download the appropriate update from Microsoft

http://www.microsoft.com/downloads/details.aspx?FamilyId=5B33B5A8-5E76-401F-BE08-1E1555D4F3D4&displaylang=en

Step 2: Determine the silent install options

Running the installer with a /? option revealed the available command line options. Of interest are the following:

/quiet
Quiet Mode (no user interaction or display)

/norestart
Do not restart when installation is complete

/promptrestart
Prompt if restart is required

/warnrestart[:< seconds >]
Warn and restart automatically if required (default timeout 30 seconds)

Use at least the /quiet option, and select which restart option makes the most sense for your environment and users.

/quiet /norestart

Step 3: Select computers to receive deployment

In the Targets pane enter the name(s) of your target computers. You may also select targets via Active Directory Organization Units (OU), Admin Arsenal Collections, .csv, .txt or .aatarget files

Step 4: Deploy

Deploy and watch the magic. Service Pack 3 is quite large and will take as long as 30 minutes to install, depending on the speed of the connection and computer.