You must have faced many circumstances when it becomes necessary to reboot the windows and you insert the windows disk in the disk drive and discover that its not working properly, frustrating isn't it? so in such a situation you can boot windows using your pendrive and for NOTEBOOK PC which don't have internal CD/DVD drive this method can be extremely helpful and booting from a pen drive takes less than 15 minutes.You need a pendrive of 4gb or more for this purpose, a PC with DVD drive and windows installation disk and remember this is only for windows VISTA and WINDOWS 7 installation so here's how it is done.
Insert pendrive in the usb port
click on START>ALL PROGRAMS>ACCESSORIES>(right click on) COMMAND PROMPT> RUN AS ADMINISTRATOR.
Enter the administrator password if prompted or click yes when the dialog box appears and enter the following commands in the MS DOS window.
in the list find the disk number of your usb and enter that number instead of red colored number in the following command, here disk number is selected as 1 see image for detail.
SELECT DISK 1
CREATE PARTITION PRIMARY
SELECT PARTITION 1
(format process may take some time)
don't close the command prompt now! now insert the windows cd in drive and see the letter of your cd drive and usb drive in "my computer" window and use those letters instead of red colored letters in following commands.
D: CD BOOT
(D is the drive letter of cd drive)
(H is the letter of pen drive)
Now exit command prompt and copy window cd content on usb drive.Your pen drive is ready and you can boot windows with it but you need to change BIOS boot priority settings don't worry it's easy just follow few more steps and you are done!
start your pc and keep pressing F2 till blue BIOS screen like the one shown in image appears
select the boot tab and make removable disk at the top of the list (you'll find CD drive is at the top) you can do so using keys as shown in the green box.
exit saving changes using the last tab EXIT
Switch off your PC and insert pen drive in it and start the PC the windows installation will start automatically.