Installing Windows 7 From a Flash Drive(works for 8 as well)

First:-You need convert your flash drive's filesystem to NTFS.
Requirements:

*USB Flash Drive (Minimum 4GB)

*Windows 7 or Windows 8 installation files.

Follow the below steps to create bootable Windows 7/Windows 8 USB drive using which you can install Windows 7 or Windows 8 easily.

Procedure:

1. Plug-in your USB flash drive to USB port and move all the contents from USB drive to a safe location on your system.

2. Open Command Prompt with admin rights. Use any of the below methods to open Command Prompt with admin rights.

*Type cmd in Start menu search box and hit Ctrl+ Shift+ Enter.

Or

*Go to Start menu > All programs > Accessories, right click on Command Prompt and select Run as administrator.

3. You need to know about the USB drive a little bit. Type in the following commands in the command prompt:

First type DISKPART and hit enter to see the below message.

Next type LIST DISK command and note down the Disk number (ex: Disk 1) of your USB flash drive. In the below screenshot my Flash Drive Disk no is Disk 1.

4. Next type all the below commands one by one. Here I assume that your disk drive no is “Disk 1”.If you have Disk 2 as your USB flash drive then use Disk 2.Refer the above step to confirm it.

So below are the commands you need to type and execute one by one:

SELECT DISK 1

CLEAN

CREATE PARTITION PRIMARY

SELECT PARTITION 1

ACTIVE

FORMAT FS=NTFS

(Format process may take few seconds)

ASSIGN

EXIT

Don’t close the command prompt as we need to execute one more command at the next step. Just minimize it.

Note:What we just did was to convert your Flash drive's Filesystem to NTFS.

Next step is to make your flash drive a bootable drive.
Insert your Windows7/Windows 8 DVD into the optical drive and check the drive letter of the DVD drive. In this guide I will assume that your DVD drive letter is “D” and USB drive letter is “H” (open my computer to verify that.).

6. Maximize the minimized Command Prompt in the 4th step.Type  the following command now:

D: CD BOOT and hit enter.Where “D” is your DVD drive letter.If your DVD drive letter is "E",then type 

E: CD BOOT and hit enter.

7. Type another command given below to update the USB drive with BOOTMGR compatible code.

BOOTSECT.EXE /NT60 H: 

Where “H” is your USB drive letter(Confirm from "my computer"). Once you enter the above command you will see the below message.

8. Copy your Windows 7 or Windows 8 DVD contents to the USB flash drive.

9. Your USB drive is ready to boot and install Windows 7 or Windows 8. Only thing you need to do is to change the boot priority at the BIOS to USB from the HDD or CD ROM drive.

To do this when you switch on your system,press the function key with the attribute SETUP (in my system,its F12),go to boot configuration/priority and change first boot device to 

USB DRIVE/REMOVABLE DISK.

Note: If you are not able to boot after following this guide, it means you haven’t set the BIOS priority to USB. If you got any problem in following this guide feel free to ask questions by leaving comment.