Is there a specific reason you want to do this?
I'm assuming you've forgotten the Windows Administrator password and are not attempting to hack into someone else's PC.
You can view most files within Windows XP from Linux. If you download a bootable linux CD like Puppy Linux
http://puppylinux.org/
You can burn that to a disc and get the BIOS to boot from CD.
Once in Linux you should have a hard drive icon on the desktop called something like SDA1 (nb. Linux doesn't use drive letters like Windows it all starts a / (root) and everything branches off from that but don't worry about that just open the icon from the desktop).
When in SDA1 you should be able to access all the windows files, documents, and everything on the computer (Windows file security is so unbelievably lame!) - in XP all your documents and settings are stored in the "Documents and Settings" folder (in Vista/7 that is now the Users folder).
You can then copy them to USB stick just plug your usb stick in and it's icon will appear on the Linux desktop. Open it and drag and drop your files from one window to the other selecting copy or move (ignore the symbolic link options these just create links to the file like Windows shortcuts).
If you are copying them to USB once done go to the USB stick icon on the desktop, right click and click Unmount to unmount the USB drive - this is the same as the safely remove hardware option in Windows, but in Linux it's more vital that you do this, or you can just shut the PC down and then remove the stick.
If you want to reset the admin password for Windows there are Ultimate Boot Discs that will allow you to reset XP passwords, or tell you XP passwords, search google for Ultimate Boot Disc (you can buy them from eBay or download them and burn them yourself).