If there is a sticker with a Microsoft licence key on the computer itself this should allow you to install the OS again using that licence. If it's a laptop then it could have a sticker on the bottom - though it may only be a licence for XP.
Thanks Geek4me i have checked it, I found a sticker with license key, but 2 digits are removed from sticker,
@Nathan already answered this on the first reply.
No you can't use one key on two PCs.
End of story, thread locked.
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