Did a bit of research for you. Look at this:
Setup process (display, logging, installation location, organization name, and so on) = Pro11.msi
So yeah, it is something to do with the installation location, and is not the cause of the problem in a matter of fact.
This is about it:
Also You could try putting the disc in, pressing Setup again, but running a Repair option. It might be that it is using the disc to get the file that is missing, storing it in temp for a while, and then your computer is wiping it. Running a repair will make sure it copies that file hopefully... Another thing...
When you installed Office 2003, In setup, did you select it in Custom settings, to install the programms "On Computer", rather than "From Disc" or something. I know there is an option for that, and coulsd be the source of the problem also!
Hope it is
Sorry about the long post.