for basic *static* screen capture, there is a button on ur keybard call print screen. press that and paste into any image editor (or just ms paint) of your choice and save.
What about ACA Capture Pro, it is the best screen capture software i have used. it is pretty good for the person who has to capture abundont images or videos from pages. furthermore, the ACA capture PRO has many enhanced features: capture all flash file from web page, create videos of your computer screen (make AVI Video/Movie), and capture any icons whatever from a file, a directory, or whole harddisk on your computer. With ACA Capture Pro's many features, you can save time and enhance your screen shots.