Hi all...I run a local non-profit and we were gifted some older computers (Pentium II's) and they are all running Windows 98. We want to upgrade them to Windows 2000 or XP. Where do I find that? What is the average cost? Do I only need one package I can install on all of them? What does it mean "OEM" ? I'm a bit lost in all this. Is it worth it to pay a local dealer $90 to install/ update each computer? Thanks !!!