I won't say it's impossible, but in the case of Office, it's more like rebuilding an engine than "tinkering." Office not only installs lots of files in lots of different places, it adds a slew of registry entries. If this is an OEM install, have you checked to see if the install files aren't somewhere on the hard drive, perhaps in a hidden directory or partition? They might not work even if you have them--some OEM installers are designed to only work on the original system--but it's worth a shot.
