DL said:
In your circumstances one licence = one PC
Thus four licences (media) required
I can not recall a time when Microsoft software licensing was something
you could easily understand and you could find license info readily
available. Still, there may be more to it than DL's answer indicates.
A business with 4 computer users may want to investigate Microsoft's
Volume Licensing/Software Assurance programs. Volume licenses start on 5
licenses, and a bundle of 5 licenses (single media package) may be
cheaper than four single licenses (each with individual media).
Businesses tend to grow, so the fifth license probably isn't a throwaway
anyway, and with more licenses the saving increases.
With Software Assurance (annual fee) you get additional training
material and support, and the opportunty to upgrade to the newest
version of the software without additional license payment.
See a certified MS reseller and/or MS website for further advice.
http://www.microsoft.com/licensing/default.mspx
Or you could check out OpenOffice. Rather simple licensing, low price
and small footprint (both the software and the documents produced are
considerably more compact than the MS products). The current production
version may seem a little sluggish in some respects, compared with MS
Office, but the 2.0 version (still in beta, with no scheduled release
date) is promising. (It still runs on Win98. MS Office 2003 doesn't.)
http://www.openoffice.org