Enterprise-Grade PC Computer Backup Program - FREE @ Veam
One of the most respected players in the world of enterprise-grade backup programs is Veeam. The company has recently announced a completely free version of its software, designed to back up individual PCs running Windows 7 or later.
Note that the installer runs to around 200 MB, so it's not a small file. It also works best if you have a reasonably fast computer, as this is a very powerful (although easy to use) product.
You can back up individual files or folders to an external USB drive or a separate NAS-type storage system. You can also back up to another part of your existing PC, but it's not recommended for obvious reasons (if your PC dies, so does your backup).
You can also back up your entire PC, and then create a bootable recovery disk. You can then restore the backup, even to a machine that has no operating system, by booting from the recovery disk and then proceeding with the remainder of the restore process.
"Veam Endpoint Backup Free" is a really nice product that's easy to use, and free of charge. If you're serious about backing up your computer, it's worth checking out