Windows 7 has "Snipping Tool" built in which is great for nearly all situations. There's no need for a different tool anymore for most people. Plus you still have <Print-Screen> and <Alt>-<Print Screen> which Windows has had since 3.1 or so. The Snipping Tool lets you highlight, draw, select any region, and save as png or jpg.
Microsoft Snipping tool also lets you take a snapshot from any programs drop-down menu.
In that case start Microsoft Snipping tool but make sure it is empty, then from any program click on the drop-down menu and just press Print-screen button on the keyboard.
This could be very useful if one has to do an instruction.
Very few or perhaps none of the other tools have this feature.
Since it inbuilt on every Windows from Vista/7/8/10 it is totally free.
Just spend a couple of minutes to learn how it works, you will find it is a very good tool.