If in your daily work in front of the PC you need to make regular screen captures, a program like Fergo Screenshot 1.2.34 will be really useful to you. It lets you speed up the screen capture process via key combinations you configure.
Apart from being able to make these captures manually (that can be all or a part of the active window), you can let the program automatically make captures at intervals, and save them (in JPG, GIF, PNG, BMP or TIF formats) in a size and resolution you decide.