Here’s a Video Tutorial on how to install Windows 8 from a USB pen drive.This is the easiest way.
Now you will need need: a USB pen drive (4GB or greater in size), Windows 8.1 disk image file (64-bit download here, 32-bit download here), Microsoft’s Windows 7 USB tool (download here) and of course a working PC.
Once you have all those, follow these steps:
1. Double click on Windows7-USB-DVD-tool.exe and click “run” when prompted.
2. Follow the on-screen instructions by clicking Next, and then Install.
3. When the installer is finished, click the Finish button.
4. Install and run Microsoft’s Windows 7 USB tool. In the subsequent window browse to the 32-bit or 64-bit Windows 8 disk image file you’ve already downloaded. Hit next.
5. With your USB stick plugged in (remember, it’ll need to be at least 4GB in size for a 64-bit install), choose USB device as your media type.
6. Select the correct removable device from the drop-down menu, then click begin copying.
7. Sit back, relax, while the USB tool formats your pen drive, makes it bootable, and copies over all of the Windows 8 files.
8. Once the process is complete, the USB drive can be used to boot a PC and run the Windows 8 setup process.