1. Contact your computer manufacturer.....
a) ask for a set of Recovery disks. The cost of a set is minimal, but money well spent. That will be your lifesaver.
b) at the same time, ask to speak to a tech person. Ask the person to teach you how to use the Recovery disks.
c) ask the tech person how to access your Recovery partition in order to restore your system.
2. All else fails, download your computer's version of Windows 7 ISO > ( make sure the ISO is the same version and same bit level ) >
burn it to a bootable DVD by using Windows 7 USB/DVD download tool >
use the DVD to restore your computer > You have to have the valid Windows 7 Product Key to do that.