screenclip
ScreenClip is a free lightweight screen capture utility for Windows.
...Copy the screenshot to the clipboard by pressing Ctrl + C. Close the screenshot window by clicking inside the upper right corner of the screenshot. No installation is necessary and the utility does not require administrative privileges to run. Start the utility initially by double-clicking on the downloaded executable file. Place the executable file in your Startup folder to have it start automatically when your computer starts.
Screenclip is a compiled AutoHotKey (AHK) script. See http://ahkscript.org/ for more details.