windows - My Notepad is not responding when trying to save

A few hours ago I was doing a research work when I finally decided to save the data in Notepad and call it a day, it isn't responding. When I press File > Save, the "Save As" dialog window appeared and it just froze there.

Same thing happened when I open another instance of Notepad, works, but also froze up when "Save As" dialog window appears.

By the way, my CPU Usage stays at 35% - 45% (after playing a game), I wonder if there's anything to do with the Notepad freezing?

My disk activity indicator isn't flashing; doesn't flash when I tried to click on it.

Have you tried restarting your computer and doing this as soon as your computer starts? You could also try restarting in safemode by pressing F8 when the windows screen comes up during startup and then try your notepad.
if either of these work, then you can figure out if you have a software or resource problem. I would also run MalwareBytes to make sure you don't have any viruses using up your resources and blocking programs.

You could also try copying it into word, or google docs to preserve it