I believe the OP is trying to ask whether installing a fresh install of XP (or any other OS for that matter) is faster from a CD-ROM or from an USB-drive, such as USB memory stick.
Theoretical max transfer speed of USB2 device is almost eight times as much as a CD/DVD-drive that can keep up constant 52x reading speed. In practice, USB2 devices are much faster to install an operating system from than CD-/DVD-disc.