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#11
You may have a legal copy which key can be retrieved using the method in Clean Reinstall - Factory OEM Windows 7 if you still have Win7 on the drive or in a backup image you can apply.
Are you using the Vista key or a Win 7 product key which was otherwise provided?
You can ask the seller for the key since it is a crime to sell pirated software. He may have a replacement key.
Otherwise you'd need to buy a Win7 Home Prem key which runs about $89 on Tiger Direct. Don't buy it from any lesser retailer.
Or you can reinstall Vista with that key using the Same steps but with the Vista ISO - Download and Create Installation DVD or USB. With such a perfect install it is a tolerable OS.