Sathishar,
If the license for XP is a retail license you are allowed to move the license from one computer to another. If the license is an OEM license, it is "married" to the computer onto which it is first installed and cannot be moved to another computer.
If retail, just install XP onto the new computer. The process of activating the new installation will invalidate the old installation on the old computer at some point in the future.