This post describes how to Install Windows 7 from USB hard disk or a thumb drive.
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. To open command prompt Go to Start Menu -> All Programs -> Accessories, Right click Command Prompt and select Run As or Run as Administrator (Windows 7)
3. Before proceeding further you need to know few details about the USB device you plugged in at step 1.
a. At the command prompt first Type DISKPART and hit enter.
(This will list all the disks in your computer. Take note of the disk number that you connected in step 1. In the screen below my Disk number is 5.)
b. Next, select your disk by typing SELECT DISK 5.
(Use the disk number you noted in the above step)
c. Next you should clean all the data in the disk by typing CLEAN and hit enter.
d. Next create a partition by typing CREATE PARTITION PRIMARY.
e. Next you need to make the disk active, so that you can boot your computer from this disk, type ACTIVE and hit enter
f. Format the disk as NTFS, using FORMAT FS=NTFS.
(This may take some time depending on the size of the USB disk you are using)
g. Next Assign a drive letter to you USB device by typing ASSIGN.
h. Now you are almost done, exit the diskpart program using EXIT command
Format 150×150 Install Windows 7 from USB
Don’t close the command prompt as we need to execute one more command at the next step. Just minimize it.
4. Next insert your Windows7/Vista DVD into the optical drive and check the drive letter of the DVD drive. I will assume that your DVD drive letter is “D” and USB drive letter is “H” (open my computer to know about it).
5. Maximize the minimized Command Prompt in step 3.g. Type the following command now: D: CD BOOT and hit enter. Where “D” is your DVD drive letter. CD BOOT and hit enter to see the below message.
6. 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. Once you enter the above command you will see the below message.
7. Copy your Windows 7/Vista DVD contents to the USB drive.
8. Your USB drive is ready to boot and install Windows 7/Vista. Only thing you need to change the boot priority at the BIOS to USB from the HDD or CD ROM drive.