Windows 7 key on the back, but is not accepted?

I got a laptop from my mother for a used laptop.

On the back is a Windows 7 key, but it does not look like it should normally look like. I have already tried this key entered on Windows, but it is not accepted.

Why can't I rebuild my Windows with this key?

I always thought that you can only use a Windows key for a computer.

But he does not look like he normally should.

You have already given yourself the answer. It is not a correct key.

On the back is a Windows 7 key, but it does not look like it should normally look like.

Either it is not or has been used, buy a key or do it the other way. XD