Apple Inc. has updated Boot Camp to version 2.1 for Windows XP and both the 32 bit and 64 bit versions of Windows Vista. Despite the Vista-oriented version of two of the updates, the patch notes specify that the update is intended to support Windows XP Service Pack 3.
The update notes also say, "This update addresses issues and improves compatibility with Microsoft Windows XP and Microsoft Windows Vista running on a Mac computer using Boot Camp. It is highly recommended for all Boot Camp users. Important: Installation of Boot Camp 2.1 is required before installing Windows XP Service Pack 3 (SP3)."
Boot Camp is the name of Appleis technology that allows dual booting into either Windows or Mac OS X on Intel-powered Macs.
You can find each of the downloads at the following links: