A clone is an exact duplicate of a partition or drive and would be useful if you just want to swap one for the other. You're probably looking at imaging which makes a compressed file or set of files which can be restored by the same program. If you're willing to pay for a decent utility, I use and like Acronis. If you want free, some here recommend Clonezilla. I've tested that one and it works but I prefer Acronis for some of it's other features such as allowing one to extract individual files from an image. In any event, these programs work by creating bootable CDs which are used to make images or restore them. Acronis can make an image from within Windows as well. To restore an image with Acronis, you can boot from its original CD or one it can make for you if installed on the hard drive. If you have the image stored on another hard drive...internal or external...you navigate to it and select it as the source. You then select the target drive from a list of what's available and just let 'er rip. It's fairly simple after you've done it a time or two.
I have a brand new computer and I just got it the way I want it. With past experience, I know the computer will crash at some point. I want to spare myself the time it takes to reinstall the operating system and software. I would like to know what is the best program to use when cloning a drive and how to reinstall that image onto that hard drive or another hard drive as back up.