Product Key and Serial Number the same?

I want to install win7 on my new hard disk (LapTop). And on the bottom side is "serial number: …". Can I install with the serial NO windows? Or can you use it as a product key?

No, you have to read the product key with a tool.

e.g. https://www.chip.de/...63752.html

Hmm like if my hard drive (where win7 was on it) is broken…

If Win7 was preinstalled on the PC, it is located on the rear of the case, with some on the bottom of a Microsoft sticker with the product key. - For laptops usually on the bottom