ALT + Print Screen (sometimes listed as PrtSc) on the keyboard will capture the active window. Paste your content into an email, Word, MS Paint, etc. afterwards.
<<Thanks - and where are the screen shots saved?>>
To the clipboard, like text when copied.
You then need to paste the output (typically via CTRL + V or from the menubar, Edit > Paste) into an application that can handle image output. Such applications include MS Paint, Microsoft Word, Microsoft Powerpoint, Microsoft Outlook (in the body of a Rich Text or HTML) email, etc.
pressing CTRL has no effect. The CORRECT answer is Print Screen for the full screen or Alt+Print Screen for the active Window.
You could also use third party tools like GadWin which will provide various options, including the selection of the key sequence, automatically saving to a file of a given type, and capturing only a rectangular view of the screen.
Further, that key sequence has been available since AT LEAST Windows 2000 and I think NT4 and possibly Win9x and it still works with Win7 and Vista.
You're right about the CTRL comment, leew... this was one of those times where I just had to... *sigh*
Windows OS
This topic area includes legacy versions of Windows prior to Windows 2000: Windows 3/3.1, Windows 95 and Windows 98, plus any other Windows-related versions including Windows Mobile.