I recently noticed a bug when you start GNU Emacs win32 after starting Windows Magnifier: Emacs' cursor becomes a single-pixel "caret" instead of the box cursor. This makes the cursor very hard to find.

I usually leave Emacs' cursor at the default (box) because this is so much easier to see, especially if you also enable blink-cursor-mode (though that's a matter of taste, I suppose). The default settings also set the cursor to a hollow box when the window (or the entire frame) is inactive.

Really, a text editor is unusable with a "caret" or bar-shaped cursor.

The following behaviors are observed with this bug:

So, the work-around for this is to start Emacs before you run Magnifier (especially: make sure the Windows Accessibility feature that starts Magnifier when you log in, is turned OFF).

As far as I can tell, there is no bug report for this.  I may file one when I get around to figuring out GNU's bug-tracker.