Wpic is a simple and free command-line tool which you can use to capture an image of a complete web page.
Of course if a web page is small enough to fit on the screen then the PrtSc key is the only capture technology you really need. Wpic, though, will grab pages of any size. The program's command-line nature means it can easily be automated. And it's based on the Chromium project, so you can be sure it'll render your target page accurately.
To use the program, you must provide the URL you'd like to grab and the name of the output file, like this:
wpic.exe -u http://www.softwarecrew.com -o softwarecrew.png
Wpic's use of Chromium means the program isn't exactly lightweight, and it can take some time to launch, download and save a full page (we ran the above command on a very fast PC with a 10Mbps internet connection and it still took 22 seconds).
Still, it worked very well for us, and if you regularly need to capture images of full web pages then wpic could be ideal.
It can be a little slow, but otherwise wpic provides a reliable and accurate way to capture images of full web pages.