From the computerworld:
Dell Inc. will charge customers up to $50 for factory-installed Windows XP on some PCs after Wednesday, according to the company's Web site. Vista Business and Vista Ultimate are the only generally-available editions that allow downgrades, and they can be downgraded only to Windows XP Professional. Under Microsoft's licensing terms, the less-expensive XP Home cannot be installed as a downgrade.
This is really funny, Microsoft spent over 6-8 years developing MS-Vista and now users are willing to pay not to use it. This clearly indicate that end users only pay when you have a better product, which is free from DRM crap, faster and less buggy as compare to Vista. As usual, I suggest you get Dell with Ubuntu Linux loaded for 100% peace of mind.