Windows XP install

[Ducati998ss]

Im having trouble installing XP on my computer. I bought everything And when i enter the serial # that came with the disc it says incorrect key. Its the one that came with the disc so im not sure why its not working. Also I tried entering other keys but nothing works. What can i do?

[AMD RULES]

did u make sure you were typing it correctly?
Contact Microsoft and see if the key is already registered...
Send it back to the vendor.....