I had a tough time with this one. I wanted to deploy it with SR3 installed also.
A) Get the Office 2K Resource Kit. Then you use it to create an .MST file, which is basically a Transformation file that you can tell your policy to use in conjunction with your MSI file for an unattended install
B) Repackage your Office with SR-1A and then SR-3 patches. You need to use the MS Installer commands (MSIEXEC). You can slipstream the patches onto your office installation by using the /P option in MSIEXEC. If you noticed, when you install Office 2K (no service release) and then you update to SR1a and then SR3, Office will ask you for the CD or installation path everytime you attempt to change something in office or have a new user and new profile created in the machine. Look up MS Knowledge Base on "Office asking for files" and you will find the Q article explaining how to slipstream the Office directly to SR-3 and it won't bug you with that ever again.
I admit, it was hard work to finally figure it out, but it was worth the effort. I can deploy Office 2K SR-3 anywhere with Group Policies and all the correct files are on the machine, so no prompting for files, especially on a laptop when it's miles away from home.
"In space, nobody can hear you click..."