Did you use any search engine?>Nestopia:
-use Nestopia UE / Undead Edition
-
set Fullscreen by options-close Nestopia
-the parameter to start a romfile:
nestopia.exe "PATH_TO_ROMFOLDER\YOUR_ROMFILE.nes"
>VirtuaNES:
-the first time, you start a romfile manually, a file named "VirtuaNES.ini" is generated
-edit the file and search for LoadFullscreen=0
-change it to LoadFullscreen=1 and save
-the paramter to start a romfile:
VirtuaNES.exe "PATH_TO_ROMFOLDER\YOUR_ROMFILE.nes"