Crazy as it sounds has the bios on the older hardware been optimized correctly ?
Does one box have a proper GPU or “onboard” ?
My spare test box (older dual core AMD) with only 2 gig ram runs win 10 just fine and ran XP x64 really well.
The server (much older dual XEON ) also runs both CREATE and desktop IDE’s just fine even with the OB GPU.
This box is just an older x4 bulldozer but on all the boxes the bios is set up correctly and any security is set to avoid ALL ARDUINO related items and they all have very similar response times in both CREATE and desktop IDE’s.
I could pull out a spare XP box single core but I already know that too will do double duty on the IDE’s with not too much overhead.
I dont think you can optimize the IDE per-se but you can certainly improve its environment.
Maybe an older IDE such as 1.6.5 would be better on the old hardware but you would loose a couple of nice features such as the precompile available in the newer IDE’s
On all my boxes the services are also tweaked so as to provide better performance and avoid running unwanted ones. BlackViper has some nice help with that.
I am not there so cleaning up and setting things to the best is something I cannot do from here without RDP or similar.
Best I can do is attach a couple of files that may have some helpful sections in them for you to try.
Arduino troubleshooting made easy.pdf (522 KB)
CLEAN UP BEFORE INSTALLING ANOTHER COPY OF THE IDE OR ARDUINO CREATE.pdf (345 KB)
There are quite a few steps to ensure the computer is safe to use again.pdf (154 KB)