I'm pretty sure you can save it from Paint with any file extension you want.
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If you want to edit or create, or in fact do anything that the pricey Photoshop does, try a FREE program called Gimp2 (I don't like putting links in forums, so Google it). I have been using it for several years. I'm not proficient, but I've used it to make some nice stuff.
I took a quick pic from my phone to make my avatar for this forum, it's small so it's hard to tell, but it's actually a cartoon of me.
It's shareware so if you're a real geek you can download the source code and make your own plug-ins and edit the program. They also accept programming from users and review it for adding to the program, so it is always improving.