depending on your operating system this may vary in windows7 click start control panel you should see system security tab in that back up then windows will ask for a back up DESTINATION location you can select either dvd or another device or in XP click start all programs accessories system tools you should see back up after the back up finishes windows will tell you your computer back up was successfull also you could right click on the back up file select properties this will tell you how many GB were used

hope this helps