Download a copy of Macrium Reflect (free).  Install it and use it to create a usb boot disk.  On a regular basis run disk cleanup and create a backup copy of your system drive on an external hard drive.  Recommend you keep the latest three copies.  You can create a backup by running Macrium under windows, to recover you will need to boot from the usb stick.  You can also run Macrium Reflect to recover individual files/folders.