Hello user,
I tried with EmEditor v11.1.7 with Windows XP+SP2, and if you right-click on Explorer, and select “Open With” > “EmEditor”, only one file is open. However, you see the same behavior with Notepad, too. If you select multiple bitmap images and select Open with Paint, the same. I think this is the Windows behavior. Please select “EmEditor” on the context menu instead.
Thanks!