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I am replacing my hard disk, because it has virus in it and also the hard drive is giving me problems, I want to know how can I use the same key when installing Windows 7 on new hard disk?

I had bought this key from eBay. So is there any procedure like de-authorize the machine first or backup some files that contain key?

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up vote 5 down vote accepted

If the hard disk is all you change, the computer will automatically be recognized by the activation software, using all the other components that are still the same.

Microsoft allows small changes to the hardware, but not big ones such as the motherboard.

So you can reuse the same key on the same machine when reinstalling Windows on a new hard disk. But leave all other hardware as-is, and especially do not dare to change the network adapter card.

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Use a tool like System Information for Windows to get the key if you don't have it. Then, upon reinstallation, you will need to re-active Windows. If you have a legitimate key (I would never recommend buying a key off e-bay - chance of getting a bad key is too great in mind), then it should re-activate without issue. Should you have issue, call the number for activation provided.

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