When you need to format Windows 7 then you need many things like: 4 GB, and make pen drive bootable, so you need the process.
Make Pen Drive Bootable
If you want Formatting and Installation of Windows 7 Or Windows 8 using Pen Drive then you need to Change Boot Order in BIOS. So see process for changing Boot order in BIOS.
Procedure For Selecting Pen Drive In Booting As Primary By BIOS:
1. Restart PC/Laptop
2. And Press F10 key when PC start start-up.
3. Then select "System Configuration"
4. Now click on "Boot Options"
5. Then find "Boot Order"
6. After that edit order and choose "USB Hard Drive" firstly and save setting.
7. After that you able to Format Windows 7 or Windows 8 using Pen Drive.
8. And install the Windows 7 Or Windows 8 OS in the PC/Laptop using the Pen Drive.
I am share method which useful when your DVD Writer not working or any other issue, so try to install windows 7 on PC/Laptop by Pen Drive.