Hi there! (first post here
I just done this recently...
All you got to do is use ophcrack (just google it) it is a linux based live bootable CD - It works great.
What I also did was follow instructions from http://www.pendrivelinux.com/2007/06...-usb-ophcrack/
to get it working from a USB flash drive, you'll need at least 512MB I used a gig. The instructions are fairly simply - but they did neglect to say the need to de-compress the ophcrack live cd ISO file.. just use 7-zip or similar.
Have fun! - now I have a flash drive on my key ring which will give me administrator access to any unguarded computer (running windows)