youre the 2nd person i've heard with this problem. It must have to do with some kind of hotkey management or "system enhancement" software that came preloaded on your new PC, or possibly some capturing/casting software, or possibly some kind of GPU driver option related to either of those which has been turned on by default. Look for something weird and seemingly useless to uninstall. If it were me, I would yank the hard disk, attach an empty one, and install a fresh windows just for testing. Then run desmume immediately to confirm that it works; then begin installing drivers one by one. If it stays working youll know it's preloaded junkware for sure.

Also possibly: fault discrete/integrated GPU switching malfunctioning. Try forcing to discrete for desmume.