I can’t find it/never had it. the laptop was a gift from the in-laws.

If i run and install Win 10, will i turn my laptop into a slab?

You won’t need it if it all goes smoothly. If something goes wrong then there is a chance you will to put it right. Just download an app to get it from your current install.

Everything which needs to be said has already been said – no you don’t need it for the upgrade, but it’s easy enough to get it from your install (it’s held in a registry key, just needs decrypting for which free apps are available).

Belarc advisor is free, trustworthy and should give you the key for your records but you shouldn’t need it

As long as your win 7 install is properly activated then you won’t need the key when you upgrade.

FYI if you want to do a “clean” install of win10 then you MUST do the standard upgrade within win7 first. That will use the old win7 license and activate win10.

Thereafter you can do a completely clean install of win10 as Microsoft keeps a record of a unique hardware ID of machines it has previously been activated on, so you don’t need to type a key in then at all.

However whatever you do, don’t do a clean install from Win10 media without activating an upgrade for
Win7 first..

Not true any more – so long as you have a W7 key. The latest November upgrade will install using a W7 license key (so long as it’s a retail or OEM one, doesn’t work with an enterprise key – I know, I’ve tried).

FWIW, having had a play around with VMs, it appears to be the motherboard UUID which is stored on the MS servers, you seem to be able to change the MAC address for example and it will still register correctly.

I can’t find it/never had it. the laptop was a gift from the in-laws.

A lot of laptops the key is built into the BIOS.