Alison,
Please follow these steps for assistance:
Step 1 is to run the utility at this link http://go.microsoft.com/fwlink/?linkid=52012, then click the Windows tab, click the "Copy" button, then paste the report into a response in this thread.
Step 2 is to look on the computer or with the retail box materials you received with the computer or with Windows to see if you have a Certificate of Authenticty (CoA). If you have one, tell us about the CoA. Tell us:
1. What edition of Windows XP is it for, Home, Pro, or Media Center, or another version of Windows?
2. Does it read "OEM Software" or "OEM Product" in black lettering?
3. Or, does it have the computer manufacturer's name in black lettering?
4. DO NOT post the Product Key that may be printed on the CoA.
Not sure what to look for? See this page for reference: http://www.microsoft.com/resources/howtotell/en/coa.mspx
For great advice on all topics XP, visit http://www.annoyances.org/exec/forum/winxp
