You are not an admin... WTF?

The other day, I received this weird error message when trying to install Office 2000 SR-1a on an SP3 Windows XP box. WTF?



I even tried an "msiexec /update data1.msp" in a SYTEM priviledged command box, same error. No info on Google although I didn't have the time to thoroughly search. Beats me...