It isn't clear what you're asking so let's first clarify that Office 2003
will *not* run on OS X. It isn't a matter of product key. PC Office and Mac
Office are two completely separate packages of software - one written for
Windows, one written for OS X.
However, your 2003 license - unless it's the Student/Teacher version -
permits installation on 1 desktop/tower system & 1 laptop as long as you
don't *use* them both simultaneously. If networked you aren't permitted to
have any of the Office apps running on one system while any Office app is
running on the other.
To run 2003 on a _Mac_ laptop, though, you need something like Parallels or
Boot Camp running Windows or a separate Windows bootup on the Mac. You'd
still be constrained to using one copy or the other at any one time.
If you have the S/T version, the license agreement is different & provides 3
product keys rather than just one.
HTH |:>)
Bob Jones
[MVP] Office:Mac