Since about the 1995 version, you must install it. Not only files need to be copied, but registry entries made, dlls registered and what else?
Since you don't have the Office CD, try this fine office replacement.
It's what I use.
I'm trying to move my copy of MS Office from my desktop to my laptop. I copied the MS Office file over to the laptop hard drive, but I can't find the installation file. WHen I try to open Outlook or FrontPage, it says the system is not configured to run that program. Where is the office.exe file located? I don't have the MS Office disk anymore, either.