One of the best ways to make a backup of your drive is to create a "disk image." This will essentially take a snapshot of the drive and make it bootable so you can restore your PC to that moment in time if your drive crashes. There are a number of third-party tools that you can use to do this, but Microsoft actually has included the ability to create a disk image right within Windows. Here's how to get to it:
First press the Windows key, type "Backup", and select "Backup settings." In the "Looking for an older backup?" section, click on "Go to Backup and Restore (Windows 7)." This will bring up the old school Windows Control Panel. On the left side of this window, click on "Create a system image." Next it will ask you whether you want to make an image on a hard disk, on one or more DVDs, or on a network location. Choose "On a hard disk." If you have a drive that is properly formatted connected to the PC, that should come up as an option to create an image on.
If all else fails, you can try one of these third-party programs for creating a disk image: