Yeah, but it does mean it is no longer the same bike. If you replace every part of a bike, even one at a time over years, it is no longer the same bike. So it all depends on what GP means by "replacing some parts". Is it entirely new computer in a 20 year old case? Or is it a 20 year old computer with a couple sticks of RAM thrown in?

Regardless, I have a hard time believing a 20 year old computer is "working like a champ". I've found the most people who say their <insert really old phone or computer> works perfectly have just gotten used to the slowness. Once they upgrade and try to go back for a day, they realize how wrong they were. Like how a 4k monitor looks "pretty good" to someone that uses a 1080p monitor everyday, but a 1080p monitor looks like "absolute unusable garbage" to someone who uses a 4k monitor everyday.