I know that my response is 10 years too late, but I just found this forum today. My solution to your problem is to find the folder with office 2003:

C:\Program Files (x86)\Microsoft Office\OFFICE11

and make a copy of the programs that I would use like word, excel, and ppt and COPY them as

excel2003.exe
winword2003.exe
powerpnt2003.exe

Then when I do Open As, I select the 2003.exe version and make sure that it opens to the old version.

Yeah I know, new office breaks old office code and screws up my PowerPoints.

Now can someone answer my question, how to I get office 2003 to run on windows 11 AND still have OneDrive working? The only solution I've found so far is to unlink OneDrive, but I've become hooked on OneDrive.

office2003-4-ever!