Revert Back to Windows 7 from Windows 10 preview

I have installed windows 10 preview in my HP laptop. I want to revert back to Windows 7 Home premium which I was using earlier. My recovery DVD doesn't work properly as it has scratches and HP recovery tools also don't help. I have the old Windows 7 product key with me. Could somebody brief about how to reinstall and go back to windows 7 now?

Thanks in advance

You can get the ISO and download/burn that to a DVD and reinstall it with your OEM product key....the only thing needed is a phone call to MS to activate it. It's no biggy I've done it quite a few times.

Here are the ISO's

Here is the phone #

Thank you :) Trying it

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