The method you choose for deploying Windows XP greatly depends on the infrastructure that's available to you. Have you deployed Active Directory? If so, Remote Installation Service (RIS) is an option, particularly if you're doing clean installs and since you have only 250 machines. Do you have a tool like Systems Management Server available? Maybe something like SiteKeeper from Executive Software? If so, you can use this type of tool to automate upgrades.
There are many other questions to consider, too. Is your network dispersed geographically? Do you have a lot of mobile users? Are you performing clean installations or upgrades? If you're performing clean installations, do users need to maintain their existing settings?
My suggestion is that you hire a consultant for a day or two to go over your requirements and infrastructure and then make a recommendation. The two-day cost of such a consultant will pay big dividends by helping you get on the right track straight away.
This was first published in February 2004