W2K would currently be(and is with respect to win OS) my system of choice. It has a much longer time in service and tends to run with exceptional stability for a Windows OS. The service packs and hotfixes are widely available. Issues and workarounds are easier to research and implement. XP still needs to mature and tends to be a very slow OS on older machines. I've seen one boot in 17 min on a 266 with 64meg of ram. Since this is for a business, M$ has a corporate program where you buy liscenses for XP Pro and can recieve the media for W2K and access the XP upgrades when you wish to upgrade. This would be a good method of selling it to the boss. Management has to pay for the OS, but not upgrade the hardware immediately and can later upgrade the OS for free after hardware and OS issues have been resolved.