" Printscreen " button on the keyboard, open Paint, Edit paste, save as...

There is still a free version of FastStone Screen Capture. Get it here: A+ Freeware - Multimedia & Design - FastStone Capture 5.3 (last freeware version) - But Jing is even better. I use both.LightScreen
Not a gadget,, there is no need for a sidebar gadget for Screenshots.
A good tool is all you need.
I would also recommend FastStone Screen Capture although not free
Still very good tool.