To capture just the active window/dialog box instead of the entire screen, press Alt-PrintScreen.
Where it goes from there, however, is another matter entirely. It's up to you to open up Paint or another image editor, paste the captured screen into the app window, and then save it. What a pain.
If you're taking many screenshots at one time, do this:
1. Open a blank Word/OpenOffice doc.
2. After doing Alt-PrintScreen to capture a window, CTRL-V in the doc to paste the screenshot.
3. After capturing all the screenshots, save the doc.
4. Save it again as an HTML file.
Each screenshot in the HTML file is named and saved automatically as a separate JPG. (Word also saves each image as a PNG).
This method is much faster than plopping each screenshot into an image editor as you capture it, and then naming/saving separately.
Later, you can use an image editor if you need to.
Here’s a better option. Command-3 on a Mac and the screenshot is saved to your desktop in PNG format.
Window’s idea of screenshots is so horrible, I’d rather use Remote Desktop, VirtualPC or VMWare on a Mac and then take my screenshots that way.
On a Mac you can capture the screen, capture an active or inactive window (even one that is mostly obscured by other windows), and capture multiple windows or a small section of a window or the desktop. You do not have to save them, they are all saved automatically. All of these captures become individual graphic files on the Desktop.
If you're taking many screenshots at one time, do this:
As mentioned above, you don't have to do any of that on a Mac. Just take as many captures as you want. and they are saved to the desktop. You can file them later, convert them to other formats, whatever.
Windows, always doing it the painful way. On the Mac:
Command-Shift-3: Screen shot is saved to a PNG on your desktop
Command-Shift-4: You get a crosshairs showing screen coordinates. Drag what you want captured and it becomes a PNG on your desktop.
Spacebar after previous: Toggles between crosshairs and a camera cursor with which any window you click on (even if it's not in the foreground) becomes a PNG on your desktop.
Adding Control to those puts it in the clipboard instead.