You can now put a bootable copy of windows on a USB flash drive and then use it as an easy way to recover your windows files if it crashes or just to bring your xp wherever.
You need 3 things for this a USB drive with at least 256mb of space, a windows setup cd, and last the freeware program BartPE.
BartPE will go through the setup cd and then create a small bootable version of windows that you can then boot on anywhere.
full article
http://tomshardware.co.uk/2005/09/09/windows_in_your_pocket/
I thought this was really cool and that it is nice to have some backup operating systems on bootable cds or thumb drives. I always have a boot cd of Knoppix, Ubuntu, and anonym.OS. However it is nice to add my Xp to that list of choices. I think that the days of staring at a setup screen are over considering how easy Ubuntu and MEPIS made it so that you can continue using the livecd while it installs. I also think that Vista is going to implement a new way of installing Windows faster than it currently does.