This short tutorial will guide you installing windows7 from a pendrive-
Make sure you have a Pendrive or USB drive with a minimum of 4 GB space and you have theWindows 7 installation DVD. This tutorial is best suited if you have a Windows 7 DVD with you else you need to change it.
1. Format the Pendrive or USB drive in NTFS format first.
2. From the start menu right click on the command prompt and select Run as administrator.
3. Now insert the Windows 7 Installation DVD and to your DVD drive.
4. Here i am assuming DVD drive as G and Pendrive as I.(Change it accordingly).
5. Now type G:CD BOOT
6. Now type this command BOOTSECT.EXE/NT60 I: to update your USB drive with bootmgr code.
7. Finally copy all the contents from the Windows 7 DVD to your Pendrive. Make sure you don’t cause any errors.
8. Restart the system.
9. Now Enter the Bios system accordingly by pressing the key delete.(This may vary some times it will be F2 or F12 or Del. It depends on the type of your system. Any how during the start up your system will display which key to press to enter the Bios).
10. Now select the USB/ Pendrive as the first boot driver.(Set the first boot priority to USB drive).
11. Now save the settings in Bios and restart and you will be able to Install Windows 7 using that pendrive.
This will definitely work... and is tested by me.......