how do you boot up with different o/s

how do i boot up with 3.5 without putting it on the flash rom, someone mentioned it can be done and said that was explained somewhere in the archives. After a good hour looking i cant find it, so can anyone tell me how to do it

steve

start the machine up while pressing "window" itll search for the .bin file you would have put on the cf card. then hit record when it asks you to . done and done