lost activation key help!

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Just bought Windows XP Pro from an internet seller. It was in unopened
box, with unopened plastic wrap inside with sticker (holographic,
looked just right) on it. Wife left wrapper inside box, husband burned
the box after we took CD out but before installing, and the wrapper
with the holographic label thingy was in the box!

Is there any way to get the key without paying for another? The product
was bought from someone over the internet, not from Microsoft or a big
company.

ie: if we go ahead and install it (since it is 'for use with new pc'
we'd have to reformat right?), but once done can we use regedit or
something I've heard y'all talk about to get the key?

I realize this is probably a big NO, but trying to redeem a husbands
relationship is kind of important :-))

Thanks for listening, anyway.

Ann in PA

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