I've recently bought a new laptop but I still use the old one for some gaming and other stuff.
Unfortunately the escape key is gone and I cannot exit some games that require that key.
How do I remap the keyboard? I'm looking for a solution but it's not clear how to do it.
Is it possible to change the keys through the registry?

You can use on-screen keyboard (Win+U) or external keyboard. Or you can use the mouse with extra buttons that supporting key remapping.
Or you can use ALT+F4 or CTRL+Shift+del to exit from game.

Try alt f4 for going out of games or ctrl alt delete, but i had problems with the Y key on keyboard and used keytweak to remap the controls on my keyboard. I believe it changes it in the registry but probably doesn't work in games then since i tried and it will always need to restart the pc when changing keys.
But then somehow my Y key started working again and made it everything back to default.
.

Yes, remapping the keys through the registry is possible on Windows 2000 and above.

There is a handy program called SharpKeys that gives you a nice user interface for that feature. You can get it here: https://www.randyrants.com/software/

Gez I didn't expect this to be so difficult.
By the way I know that I can exit applications with a combination of keys, but the problem is that I cannot save in some games if I don't go back to the menu screen, which you usually reach through the escape button. Cool. Is it doable for noobs? Because I'm a noob wih this alien technology.

Here's a workaround:
Press the Windows key while in a game or Alt+Tab,
Go to Settings,
Ease of Access,
Keyboard,
Turn on on-screen keyboard (different from the usual Windows on-screen keyboard),
Click on Esc which is not available in on-screen one.

What happened to the warranty?

It's very easy to use, just give it a try.

I don't think that will work. I will give it a try though, right now.

The warranty? Dude, this laptop is from 2013. I started working with it (copywriting), that's why I wanna keep it.
Also, I got fantastic games on its drive.

OMG OMG it worked. This Lebowski dude is the best. It is not the best workaround in the world but I mean, I cannot complain. Thanks guys.

Long shot, but is it a Win 10 laptop?

Also, I just checked, and the shortcut for it is Windows Key + Ctrl + O on Win 10.

Your method worked man! It's a Win 10 system by the way.

Glad I could be of help :D

This post is very confusing. You mention two separate computers, which one are you having issues on? When you say the escape key is “missing” what do you mean, it’s not present at all, the key top has been lost, it’s a foreign keyboard and you can’t find it? I have yet to see a keyboard which doesn’t have an escape key (not saying it doesn’t exist, just haven’t seen one), but if you need that key, perhaps getting one with that key might be beneficial in this and other ways. For instance, for some time I used an American layout keyboard, it is not worth it, bin it and get one that suits you (goes for laptop or desktop). Really not understanding what the issue is here?

The escape key is broken on my older computer. So I cannot exit or pause some games which require that key.
I cannot explain myself better than this because my English stinks.
I don't want to be rude but other guys clearly understood what I mean, so maybe you cannot read well or you have a weird accent in the UK (I mean, we all know that). In any case man, we have already found a workaround for my problem.

You also can buy A usb keyboard too and plug it into your laptop and Disable your laptops keyboard it's a good workaround!

Are you crazy? I'm Italian. I'm too lazy for that.
The on-screen keyboard is the best solution for me at the moment.