Once I tried to install Windows 10 on my Thinkpad R60 before I upgraded it (Contained an ancient Intel Core Solo processor and 1gb of ram). The operating system would freeze just trying to open the start up button, Windows 7 ran okay. The system ran fine with XP (Still had to use caution, especially with web browsing because it was so resource hungry), Windows 2000 w/ Blackwingcat's kernel extensions wasn't very stable and was still recourse hungry like its younger brother xp. LXLE Linux was probably the best choice overall. Video playback was OK at 360p.
I didn't even try to install Windows vista or later on my Dell Latitude D600, its processor was barely weaker than my Thinkpad R60's before I upgraded it and currently has the same amount of same (1gb). My Dell Latitude D600 is super unstable with Windows 98 despite installing all the drivers (If you haven't read my topic of doing so). It ran well with Windows 2000, the D600 seems very problematic in general though. In XP, the broadcom wireless driver made the os crash when I shut it down because of a sys file. If I deleted the file, xp wouldn't crash but then I lost the ability to connect to wireless. I'm gonna try dual booting 98 with Puppy Linux in the future.
Played around a bit with my grandmother's low end HP 2000-2d49wm laptop from 2011. Boy, that thing was SUPER SLOW! My Dell Latitude D600 is faster!!! HP literally forced Windows 7 on that thing and used gave it 4gb of ram just so it wouldn't look bad. CPU usage was 50% idle on Windows 7! Windows 7 had issues after reinstalling it; aero refused to work despite having the driver installed. The official dell site mentioned no support of
Vista or XP, but those two worked. Windows Vista overall preformed better than 7 and its aero actually worked. Mint Linux was a bit sluggish, but solid. Windows XP gave the CPU a massive break; CPU idle was 3% on average. Despite that, web browsing and such were still sluggish on the system. The oddest thing about the laptop is the fact it ran minecraft at 20fps at completely lowest settings, about the same amount my Dell Latitude e4310 laptop with an i5 CPU. In the end, since I had too many laptops I donated it to a local church w/ Windows XP.