Backing up to external usb drive

Hi all, new member to the forums, and new into IT in a school!!! so ill probebly be asking for a LOT of advice! ;-)
what im looking at doing is making an image of a laptops hard drive and putting it onto a external usb hard drive i have (1tb)
hopefully this will make my job easier in the future, when teachers/pupils screw them up!
what software would you reccomend for this? (hopefully as cheap as poss)
at the moment ive spent a few hours setting a new samsung laptop up with all the relative proxys/software etc and im making an image as i speak using the built in samsung recovery solution 4, ideally this would be something similar that i would be looking at but of course to back up anything not just samsungs!

hope this all makes sense

thanks in advance!

Never used it but I am sure a lot of people will recommend FOG - A Free Cloning Solution | Free Security & Utilities software downloads at SourceForge.net

have a look at "the ultimate boot cd" for a few other options , but FOG is good if you have the skill and resource to implement.

Rob