Licenses for Office 2003 pro

I have users that are using copies of office 2000 pro. I want to get everyone legal ASAP. The problem is that only certain people need the full blown version of Office 2003 the others only need access. I got a quote from dell for 25 licenses for around 11,100. Not too bad but the VP wanted a cheaper solution. So I thought about upgrades, only question that popped into mind was, do I have to have the office CD I upgraded from for each pc? Upgrade would be the way in my opinion if we don’t have to show the actual CD. (Not ethical but I?m working with what I have) Would I be considered legal at that point, From a Microsoft point of view?