article [microsoft.com]
OEM software licenses cannot be transferred from one computer system to another, even if the computer system on which it was originally installed is no longer in use.

XP Home EULA [microsoft.com]:

13. SOFTWARE TRANSFER. Internal. You may move the Software to a different Workstation Computer. After the transfer, you must completely remove the Software from the former Workstation Computer. Transfer to Third Party. The initial user of the Software may make a one-time permanent transfer of this EULA and Software to another end user, provided the initial user retains no copies of the Software. This transfer must include all of the Software (including all component parts, the media and printed materials, any upgrades, this EULA, and, if applicable, the Certificate of Authenticity). The transfer may not be an indirect transfer, such as a consignment. Prior to the transfer, the end user receiving the Software must agree to all the EULA terms.

The retail veriosn of Windows has more flexibility in terms of licencing. With OEM you get what you get and it's up to the vendor to supply you with media. MS won't help you there.

What are the requirements to apply for an academic license and how much does it cost?