How to create TMG with SP1 your source bits for installation? (slipstream)

To install TMG, then SP1 then RU1 for any reason (let’s say to support Exchange 2010 SP1 publishing) is a long way drive!

I found the below way to install the slipstreamed source of TMG with SP1 in one DVD. Follow the steps as shown below to end up with the upgraded copy

ServerManagerCmd.exe -inputpath ^<DVD_path^>\FPC\PreRequisiteInstallerFiles\WinRolesInstallSA_Win7.xml -logPath C:\Windows\TEMP\TMG-Prerequisites.log

Prepare a Forefront TMG SP1 slipstream DVD with the following steps:
1. Copy the Forefront TMG DVD and the Forefront TMG SP1 MSP file to a local drive on the target computer. For the purposes of this example, let’s assume this is c:\temp\TMG.
2. At a command prompt, type the following command and press ENTER.
  msiexec /a c:\temp\TMG\FPC\MS_FPC_SERVER.msi /p TMG-KB981324-amd64-ENU.msp /qb /L*v c:\tmg\log.txt
  When the operation completes, you will have a full installation of Forefront TMG already upgraded to Service Pack 1.

Enjoy.