How to make backup for External Hard Drive?

Honestly the easiest way is to just get another drive that can hold all the data of the original and copy it to it. No software necessary. You're just backing up data, no big deal

Alright Let me be clear about what you want If you want to make an exact copy of your hard drive file for file you wont just be able to go and get a few files off it when you want you will have to make a disk or use your original windows 7 install disk by changing the boot order in the bios to actually re install this backup. There are other third party software that can do this but windows 7 makes this really easy and I don't trust someone else to do it correctly. It really would suck if you were riding on this and then 2 months from now figured out you made a mistake. Anyhow go to control panel - System and security - backup and restore - Create system image. select your drive might fit on your pen drive however not all of them work for something like this no matter how you format them. Also if you have another completely empty partition you might be able to install it on that which would be nice considering a external hard drive is more prone to being damaged. After following all on screen instructions make a system repair disk.