Sascha Trowitzsch, fellow Access MVP went to a lot of work figuring out how to create an Access 2003 runtime with SP3 and the combo box hotfix. See How to build a deployable Microsoft Access 2003 Runtime with integrated Service Pack 3 which will download a DOC file.
Do not miss the existence of the adminexecute.idt and work with the AdvtExecuteSequence.idt. As did someone who shall remain nameless. Ayup, your dumb*ss blogger.
The Microsoft Access (Office) Developer Edition FAQ page at my website has been updated.
Also note that Microsoft has closed the security hole where the unpatched version of the Access 2003 runtime would not get updated with SP3 by Microsoft Update. The problem though is that Microsoft Update wants to download the entire 100 or so Mb Office 2003 SP3. Not the ideal solution but ok for folks on high speed Internet. Of course this would not update the Access runtime with the KB945674 hotfix which fixes the combo box problem.