Here you will learn the step by step process to create Windows 8 bootable USB.
This process is quite easy to follow and anyone handling computers go through it. This process is already tested on the HP Laptop running Windows 7 Home Edition with all updates.
Step 1: Download and Install Microsoft’s Windows 7 USB/DVD Download Tool
[Microsoft Store Link]
Click on Run to install.
Click next to continue the installation process.
Click Install, to begin the installation.
Click finish, to close the dialog box.
Step 2: Download Windows 8 server or workstation .iso file from Windows Dev Center.
Step 3: Connect the USB flash drive having at least 8GB or greater storage capacity in a USB port on your computer.
Step 4: Launch Windows 7 USB/DVD Download Tool by clicking the shortcut present on the desktop which was created in Step 1.
Step 5: Choose the Windows 8 .ISO file which we downloaded in Step 2.
Browse the path where you have saved the download file.
Now that the ISO file is selected, click Next
Click on USB device.
If you have not yet attached your USB stick, then plug it to your machine and then click on the refresh button 
The plugged in USB drive will be displayed, click on Begin copying
Note : You need a USB device that is at least 8GB.
It will first format the USB drive then it will copy the Windows 8 installation Files. If you have important files on the USB drive copy & paste it to another location.
Click Yes, to start formatting.
It will start formatting.
After formatting it starts copying the installation files.
Finally Windows 8 USB drive become bootable successfully. You can click close button ( X ) to finish the process.
Files required for Windows 8 Beta Installation.
If you want to start the setup, double click on setup.exe and follow the Windows 8 Beta Setup installation wizard
Note: You can use this USB device to boot your laptop or system, but make sure you select USB boot option while booting.
Another method using DISKPART:
Start a command line utility called diskpart.
This can be done directly from start/run or from a command prompt. Comments are between {}.
diskpart {This will start diskpart from a command prompt}
list disk {This will list all available disks in the system}
select disk 2 {This will select your usb disk, if it is called 2 in your system}
clean {This will erase ALL information on the currently selected disk}
create partition primary
select partition 1 active
format fs=fat32
assign
exit
When you are finished with diskpart, all you need to do is copy all files from your Windows Server 8 Beta installation media to the usb disk.
xcopy e:\*.* /s/e/f g:\
{ E: Drive E contains source files of Windows Server 8 Beta and where G: drive letter for USB drive.}
Conclusion:
Using above procedure you can prepare Windows Server 2008 / Windows Server 2008 R2 / Windows 7 / Windows 8 Beta bootable USB device.
MYOUSUFALI # Windows Blog 