At present you don’t need to burn DVD and wasting your time and money. Now you can easily install the windows operating system through your Pendrive/Flash drive. Installing Operating System from a USB Pen drive/Flash drive has various benefits. First of all, the overall speed of the installation process will increase significantly, carrying a USB stick is much more convenient than a DVD, and finally it becomes possible to install the OS even on those systems that do not have a DVD drive, such as a notebook.
In this tutorial I am going to show, how to create bootable USB flash/Pen drive of any operating system like windows xp, windows 7,�windows 8, Ubunto, Linux etc. To create bootable USB drive you need minimum 4 GB USB drive (It depends, which operating system you want to boot and the size of ISO file).
Step 1: Download�UNetbootin�(you can download this from here)
Step 2: Format your flash drive/Pen drive as FAT32.
Step 3: Run the downloaded software (UNetbootin)
Step 4: If using Windows, select an ISO file which you want to bootable and select the target USB Drive , then reboot once done.
(If your USB drive doesn’t show up, reformat it as FAT32)
(If your USB drive doesn’t show up, reformat it as FAT32)
If using Linux, make the file executable (using either the command “chmod
+x./unetbootin-linux, “�or going to Properties->Permissions and checking “Execute”), then start the application, you will be prompted for your password to grant the application administrative rights, then the main dialog will appear, where you select a distribution and install target (USB Drive or Hard Disk), then reboot when prompted.
Step 5: After rebooting, if you created a Live USB drive by selecting “USB Drive” as your install target, press the appropriate button (usually F1, F2, F12, ESC, or backspace) while your computer is starting up to get to your BIOS boot menu and select USB drive as the startup target; otherwise if there’s no boot selection option, go to the BIOS setup menu and change the startup order to boot USB by default. Note that Live USB drives are bootable only on PCs (not on Macs). Otherwise, if you did a “frugal install” by selecting “Hard Disk” as your install target, select the UNetbootin entry from the Windows Boot Menu as the system boots up.
If you can’t Boot your USB Pen drive/ Flash drive by this, Please follow the Step of the below (Only Windows).
(You also can create Multiboot USB drive by this way)
Step 1: Download “Yumi” Multiboot USB Creator (Click here to download)
Step 2: Run “Yumi” �Multiboot USB Creator.
Step 3: Click “I Agree”
Step 4: select the target USB Drive on “Step 1″ of Yumi
Step 5: Trick the option of “Format D:E:FG: Drive (Erase Content)?”
Step 6: Select Distribution from the box of “Step 2″ this software.
Step 7: Add Yours .iso file and click create button.
Step 8: Wait till bootable done. After boot, restart your PC and Install your Operating System 
If you want to create �a Multiboot USB drive, Run Yumi and follow the step. Then, Run the tool again to Add More ISOs/Distributions to your Drive �and Restart your PC setting it to boot from the USB device. Select a distribution to Boot from the Menu.