I use FastStone Image Viewer (free) because it not only converts, but resizes, renames, etc. I don't know how large your Paint jpg file turned out to be, but SCARM created a 61.7Mb file that is 5003x4305 for a layout posted recently. Viewer shrank that to 137kb and 1024x881 (my choice on the width) to make upload quicker and easier.