How to remove or deactivate my windows 7 licence on one computer and use it on another [duplicate]

If it was an OEM license (came with the computer from the manufacturer) you can't do this. If it was a retail license (you bought it boxed from a retailer) then simply format the old computer, install it on the new computer. If it comes up saying it may not be genuine, there will be a phone number you can call which will get you to a rep. Explain to the rep and they will have you type in a new number.

if it is a reatil copy, you are perfectly entitled to do this.

you may have to contact a Microsoft representative and explain the situation, should the activation fail.

while it is possible to backup and restore the Windows 7 activation files, you may end up with a 'stained' license, MS don't like tampering with the product activation.

Try activating the license on the new computer. If activation fails, call Microsoft Product Activation (866-542-3062) or Customer Service (800-642-7676) and tell them you changed the hardware on your computer and it deactivated itself. They will re-enable your activation without grilling you with any questions.