Have you considered using the Oval Marquee tool? You can hold down SHIFT and ALT/OPT to force the tool to create a symmetrical shape (circle) that's based at the origin point. This works in all versions of Photoshop that could possibly run today.
I was aware of this one but I get a thick black circle when I do this and cannot
RE adjust he thickness of the line (only the center color can be adjusted thought there might be a way I was not aware of. FYI Im working on a MAC Thanks Larry