Create a bootable USB stick from ISO, much like UNetBootin for Linux:

"Aris" has created a small utility exclusively for AskVG readers which creates a bootable USB drive to install Windows Vista, Server 2008 or 7.

Prerequisites:
  • A USB Drive (4 GB or more)
  • Windows Vista, Server 2008 or 7 ISO image or DVD
  • Host OS: Windows Vista (SP1 or SP2), Server 2008 or 7

Get it at Tweaking with Vishal