Recover Windows XP product key from slave drive

A few months ago my computer's hard drive corrupted and I was forced to move to my old computer. I was able to use the corrupt drive as a slave and can view all my files without problems. I am, however, considering buying a new hard drive and starting anew. However, I lost my XP product key, which is for the corrupted drive. Is there anyway I can recover the key from the slave drive? I know programs like magicaljellybean can recover keys, but only for the machine being used.
 
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