I've been using MSpaint for my circuit diagrams since it was called Pbrush.
One reason that i stick with it is because every PC on the planet can display a BMP file.
Straight from the box.
Sorry to say it, but get real: Micro$oft Paint is a deficient, fairly brain-damaged tool to be using at this late stage of the game.
Meaning that there are such better programs available that there's no excuse to use this "default" picture editor.
So far as formats native to the PC go, JPG and GIF are also just as universally-recognized as BMP. Moreso, really: most people wouldn't know what to do with a BMP, but all web browsers out there happily display GIF, JPG and PNG graphics.
Most of my diagrams are quite small, and when converted to Black and White they dont take
up much more memory than a Jpeg.
With Paint Shop Pro, I can create a compressed 16-color GIF that will be at least 10 times smaller than any JPG (16 million colors). Can you do this with Paint? Maybe, but I've never been able to figure out how. PSP makes it simple.
I do have some minor problems with the shading when using the latest MSpaint.
For some reason it won't copy and paste, but it seems alright on the older versions.
Just for the sake of comparison, with Microsoft Paint, can you
1. Copy and paste images with transparent backgrounds? (very handy for pasting in bits and pieces in a drawing where you don't want to disturb existing elements)
2. Handle background transparency
at all?
3. Easily resize/resample a picture (and do it in units of pixels as well as percentage)?
4. Easily convert numbers of colors (up or down)?
5. Edit GIF palettes? (Very useful for getting rid of various dithering artifacts, etc.)
I'm pretty sure the answer is "no" to all of these.