windows 10 product key

I need help before I start pulling my hair. I had to install windows 10. I still have the CD from way back when we were able to get it free. We did not get a product key but if I remember there was one key, but I am not sure. Now before it will install they need the product key. What can I do. I would appreciate an answer if someone has it. I will whoever can help me a bottle of Jack Daniels.

What do you mean you HAD to install W10 ?

If you don`t have a key you`ll have to buy one, or use a 7 or 8 key as suggested.

Thanks to all of you for your response. I finally got it installed and this is what happened. When I would get to the page to enter the key, it had nothing at about having another disk or any other link. It did have a link that gave me the option of doing it later so I clicked on that link. I would then click on “Next” which seemed to work, but after a few more pages, it brought me back to the page to enter the key. I don’t know how many times I went back and forth from one page to another but it must been 8 or 10 times. After I sent my question to the forum I tried it again and it finally went through. Something like,”not now” so I would click on that and in a few minutes the same page would come up asking for the key. Edwin you said something that made me stop and think when you asked me if this was the same machine that I had when installing the original widows 10 and the answer is no it was a different machine. Maybe that’s the reason I had problems. But as they say, “All’s well that ends well.”

I have never seen any OS that makes you add a key during the install, it`s always an option. You always have at least 30 days to enter a key.