Make a clone of the drive. There is lots of free and paid backup software out there that can do it. In order to restore, you either need a cloning/backup program that can create a rescue disk or you could clone from a working system, then swap out the OS drive for the cloned drive.
That would be not so much a backup, but more of an image when you include the OS. A cloned image is the most effective way to effectively backup a 'boot' or 'C' drive.
The image is the exact replica of everything on a given hard drive or solid state drive on the PC at a given point in time. You make an image of each drive separately. If you need to restore, you restore the drive in its entirety if and when necessary. It usually takes more time than a backup, but is the best way to back up a boot drive. If you can afford to keep a spare disk around, you can just keep an image on the spare disk and replace the old with the new as necessary. The Apricorn Sata Wire USB 3.0 Kit:
is really easy to use and will do this for you. It says 'Notebook' in the title of the product, but it works for desktops as well.
I would treat the external drive separately unless you are running applications from it. The external drive can be backed up using a basic file copy method and can be scheduled. There are some backup programs that allow you to schedule backup or run a backup only when files change on the drive. Windows 7 comes with this basic functionality.
thanks guys. i was reading this http://notebooks.com/2011/02/16/how-to-move-windows-7-to-a-larger-hard-disk/ And it seems like the thing i need to do. only problem is i don't have a windows 7 installation disk or recovery disk. i bought my computer a little while back and the guy never had/gave me one of these (yes it was second hand.)