A friend of mine still uses a cracked version of WinRAR from over a decade ago. I said he should just install 7zip and he looked at me like I was crazy.
If it makes you feel better: the key i've used is probably 8 years old and i'm so broke i was in actual prison yesterday because i couldn't pay for a parking ticket
Take a look at https://github.com/massgravel/Microsoft-Activation-Scripts if you want to see some interesting methods of getting around the license issue for more recent versions of Windows. It's helpful if you can't find your legitimately-owned key which I'm sure you definitely have.