Although there are many articles are available on the Internet but no one give the complete guidelines, So i write this article and describe the most efficient way to install any Operating system from USB Pen/Flash/Thumb Drives.
You can do it by any one of the two methods:
- By using a third party Software's.
- Without using any third party Software’s.
Method 1: By using a third party software.
If you want to just install an Operating System from USB Pen Drive without going into deep then this is the best method for you.
a> For any Windows Operating System:
WinToFlash :This is the best software for installing any Windows Operating System from USB Pen Drive and also it is very fast and simple to use and also support LiveCD.It will work without installation. 
For stepwise instructions of using this software see the article How To Install Any Windows Operating Systems From USB Pen Drive Using WinToFlash.
b> For any Linux Operating System:
UNetbootin :Unetbootin (Universal Netboot Installer) is the best software for installing any Linux Operating System from USB Pen Drive and supports almost all version of Linux and also very easy to use.It is available for both Windows as well as Linux.It will work without installation. 
For stepwise instructions of using this software see the article How To Install Any Linux Operating System From USB Pen Drive Using UNetbootin.
c> For Google Chrome Operating System:
For installing Google Chrome Operating System see this article How To Install Or Check Out Google Chrome Operating System.
Method 2: Without using any third party Softwares.
You can install an Operating System From USB Pen Drive in a number of way but many of them are very complicated or time consuming and it is better to use software’s instead of using these methods.So here i will discuss only the easiest method.Where this method are not applicable there use the softwares discussed above.
For installing Windows Xp, Windows Vista or Windows7:
First of all insert your USB Pen Drive and Windows Vista or Windows7 installation Disk.If you are a Xp user and you don’t have a Vista or 7 Disk then you have to use softwares discussed above.Here my CD/DVD Drive is G: and USB Drive is H: If your Drive letters are different then replace it with your own.
Now for Windows XP simply type CMD in the RUN prompt and hit Enter and for Windows Vista or Windows7 , Open Start Menu write ‘cmd’ and Right Click on ‘cmd.exe’ and then click on ‘Run as administrator’ (shown in figure) and enter the password if needed. 
Now in Command Prompt enter the following Commands:
>DISKPART
> LIST DISK
(Note down carefully the Disk Number of your USB Drive by checking the size of Disk, generally it is ‘1’ ) (suppose your disk number is ‘#’)
> SELECT DISK #
(where ‘#’ is disk number of your USB Pen Drive)
> CLEAN
> CREAT PARTITION PRIMARY
> SELECT PARTITION 1
> ACTIVE
> FORMAT FS=NTFS
> ASSIGN
> EXIT
Below is the exact output of above Commands shown in Command prompt. 
Now again in Command Prompt Enter the following Commands:
>G:
(where ‘G’ is the CD/DVD Drive letter in which vista or 7 DVD is inserted.)
>CD BOOT
>BOOTSECT.EXE /NT60 H:
(Replace ‘NT60’ with ‘NT52’ for Xp.That is in case of Windows Xp the above command is as >BOOTSECT.EXE /NT52 H: )
(where ‘H’ is the USB Pen Drive letter.)
>EXIT
Now Copy and Past the installation (Xp,Vista or Windows7) CD/DVD contents in to USB Pen Drive or Extract ISO in to Pen Drive and now your Pen Drive is ready to Boot and install Operating System in any Computer.
Just insert the Pen Drive in the computer in which you want to install Operating System from Pen Drive, then restart the computer and modify the BIOS settings if needed (enter in to the BIOS setting by pressing the appropriate key (generally ‘F2’ or ‘Del’ or ‘F10’) at the instant when computer is just ‘ON’ and change the Boot order and set USB Device at #1 (highest priority).Then save and exit) and continue the installation as usual.
