Hello Kim14,
Help us help you by providing a little more for us to work with. What are the circumstances surrounding the situation?
Download and run the Genuine Diagnostics tool found at this link
http://go.microsoft.com/fwlink/?linkid=52012.
Run the Tool, click "Continue" then click the "Copy" button. Return to your new Thread and Paste the report into the thread along with a detailed description of the issue you are experiencing.
Please also post the error code you get (if any) when you validate by clicking "Validate Windows" here: www.microsoft.com/genuine. The error code will be gray and in brackets at the end of the message on the page that says validation failed. (It'll look something like this: [0xC004C000]).
For great advice on all topics XP, visit http://www.annoyances.org/exec/forum/winxp