So... I still have Q4OS on this ThinkCentre, since I'd rather keep it just in case. Today I also tried to install Windows 2000 on my other laptop (the one with Windows XP), but it ended up with 2000 refusing to install, and when I tried to boot back into XP, I got a message saying the system couldn’t be found.
Just great...

PS.: Since I’m no IT expert, I used Gemini to help me with all this—and interestingly, it handled Q4OS very well; it’s just that Windows 2000 is too clunky for my laptop, XD