People rushing out to buy Windows XP on Thursday may be surprised by the hefty package of downloads already available for updating the brand-new operating system. Depending on the version of XP--Home for consumers or Professional for businesses--people will be assailed with 20MB or more in downloads. Some fix security holes, others resolve glitches and a few add new features. Regular updates are something consumers may have to get used to with XP, which offers more of a "push" method of delivery than the "pull" function found in earlier Windows versions. With the new OS, Microsoft for the first time has the capability of sending updates proactively to customers.