Few things you can do are: 1) contact vendor you bought it from. 2) contact microsoft and see they would give you another key. 3) buy another XP copy :(

Complain To Microsoft

From Microsoft http://support.microsoft.com/kb/310637 This issue can occur if one or more of the following conditions are true: • You did not enter the proper product key. • Anti-virus software is running during Setup. • The installation compact disc (CD) is damaged. • You are installing Windows XP Service Pack 1 or Service Pack 2 to a second partition on your hard disk. • You started the Windows XP service pack update Setup program from within Windows XP. RESOLUTION To troubleshoot this issue, perform the following steps in the order that they are listed, testing between each step to determine if the issue is resolved: 1. Verify that the product key is correctly entered into the Product Key boxes. Note If you are unable to locate your product key, or if your product key label is damaged, contact Microsoft Product Support Services. For more information, please visit the following Microsoft Web site: http://support.microsoft.com/contactus/?ws=support (http://support.microsoft.com/contactus/?ws=support) 2. Verify that your anti-virus software is not running when you run Windows Setup. For information about how to disable your anti-virus software, view the documentation that is included with your anti-virus program, or contact the manufacturer of your anti-virus program. 3. Disable the anti-virus settings in your computer's Basic Input/Output System (BIOS) before you start Setup. For more information, view the documentation included with your motherboard or computer, or contact the manufacturer of your motherboard or computer. 4. Verify that your installation media is not damaged. If it is, replace it. 5. Verify that the computer's system date is correct. For information about how to check the date in your computer's CMOS settings, view the documentation included with your motherboard or computer, or contact the manufacturer of your motherboard or computer. 6. Try starting Windows without loading extra drivers and programs. This provides as clean an installation environment as possible. After you "clean-boot" your computer, rerun Setup. For additional information about how to start Windows with a minimal set of drivers, click the following article numbers to view the articles in the Microsoft Knowledge Base: 192926 (http://support.microsoft.com/kb/192926/) How to perform clean-boot troubleshooting for Windows 98 267288 (http://support.microsoft.com/kb/267288/) How to perform a clean boot in Windows Millennium Edition 310353 (http://support.microsoft.com/kb/310353/) How to perform a clean boot in Windows XP 7. Install the operating system from a command prompt instead of from within the Windows environment. 8. Copy the installation files from the CD to the hard disk, and then run Setup from the hard disk. 9. If you are upgrading from Microsoft Windows 98 or Microsoft Windows Millennium Edition (Me), use the ScanDisk tool (Scandskw.exe) to check your hard disk for errors. To do this, click Start, point to Programs, point to Accessories, point to System Tools, and then click ScanDisk. For additional information about how to run Setup from a command prompt, click the following article number to view the article in the Microsoft Knowledge Base: 307848 (http://support.microsoft.com/kb/307848/) How to start Setup from MS-DOS in Windows XP 10. Use the number keys on the keyboard instead of the numeric keypad to type the product key. When you install an international version of Windows, Setup may use the US keyboard layout rather than the correct international keyboard layout. For example, letters such as Z and Y that are in one position on the German keyboard are in a different position on the US keyboard. In this case, type the German Z where the product ID has a Y.

PANIC

Call micorsoft. this happened to me once before during the installation of XP on a new hard drive. I called they made it work.

If you have limewire try to download it from there because that is what I did and it took me three different codes then finaly I had got it. And then complain to Microsoft.

Return Windows and order an Ubuntu cd.

If you call microsoft they will give you another number. But only if the copy is legit. If it's not legit search online or through p2p programs for a valid (or invalid) key.

If your copy is legit then I would contact the vendor and request a new disk or contact microsoft directly and be prepared to be on the line for a good while. I have seen issues like this before and it wasn't a problem with the key as it was the disk was faulty.

Sue Microsoft. If they win, Switch to Linux.

I'm having the same problem but a friend of mine said there have been occasions where the CD key that came with certain XP's were never really registered into their database...