I would think your computer is ok. Here are a few thoughts.
I will assume that your going to dedicate this PC to CNC. Start by only having Windows and Mach.
No other junk , like virus proctection or other software. It could then be PC hardware or something in windows.
Do the driver test and if need be open the windows Task Manager and see what processes are running.
Now now find out what each one is and one by one turn it off or nodify it and see if that process was the culprit.
DONOT...DO NOT TURN OFF THE ONE FOR THE MONITOR, SINCE IF YOU BOOT BACK UP YOU WILL NOT BE ABLE TO SEE THE
MONITOR! This is a rather easy, PITA, if you don't know what your doing!
Maybe someone will have a specific that will just take care of what's needed.
Each PC can have a quirk sometimes, we have tried probably 10 different ones from dead dogs to high end machines and got them all to work. The Dells with on-board graphics suck!
LOL,
RICH