I remember having a defective hdd in my PC. I brought the pc to the shop, where I bought it from to get it replaced under warranty. They told me they couldn't restore my data (I had backups) and asked if I wanted them to install windows on it. When they asked for my key I was like "FC..." and they responded "ok, we know that one, no need to spell it out" and proceeded with the installation
I don't know if it still works, but I found a "cheat" for free windows back in the day that I even upgraded into 10 with lol
My friend had an "upgrade" code for XP that he gave me, so when I installed windows and tried to use the code it gave me the whole "this is an upgrade code not a new code" kind of message. I rebooted the PC and used the same installer to "upgrade" my newly installed windows XP to windows XP. Same install, just did it again basically. It then accepted the code as valid lol
For a while you could just remove all the permissions from the activation nagware on a trial install and it would run fine, and you'd even get updates. At some point they added some service which would periodically check those permissions and revert them, and I was never able to figure out what that process was.
Which means that there is apparently now a hidden user and access tier which exists solely to monitor windows system permissions, and I feel like this is my most noteworthy legacy in a small way.
I've typed those letters SO many times. I remember being shit faced drunk in high school and getting a call from a friend who was installing Windows XP but forgot the key, because he just assumed that I could recite it. Which I could, and still can, 20 years later.