Step 1: Download windows 7 iso file and burn it to cd.
Step 2: Install cd to pc and then restart your pc.It will ask to boot from device then press “Enter”.
Step 3: Select time format of your country.
Step 4: Click “Install now”.
Step 5: Click on “Accept the agreement”.
Step 6: Click on “upgrade” to have only windows 7 or Click on “custom or advanced”.In this image advanced is selected.
Step 7: Wait for some minutes when the windows is being installed.
Step 7: Wait for the computer to restart.
Step 8: Wait for pc to restart and update the registry setting.
Step 9: Wait for pc to install windows,Then it will restart
Step 10: After restarting your pc will prepare for running.
Step 11: Write your username and password.
Step 12: If you don’t have product key then “off” automatic updates.
step 13: Install softwares that you need.