[PrntScr] copies the screen to the clipboard _exactly_ as you see it.
Do a Print Preview to get your drawing to fill the screen, screenshot it, and then you can paste, edit, crop, etc.
I usually use IrfanView as a lightweight image handler for doing quick paste - crop - save sequences.
Anything else can be used for more advanced editing. I find Paint.Net to be user-friendly, and have dabbled some with Inkscape as well.