new hard drive need help

ok i got a 40gb hard drive, i now its not that much and my computer has a 4.3gb hard drive. what i want to do is transfer all the files from the 4.3 to the 40 so when i put the 40 by its self in the computer it will start up like it does with the 4.3
i only want one hard drive in the computer i dont want a master and a slave or spare. i just whan the master
right now both hard drives are in my computer and both are working find. the 40 has been formated and health.
so what do i do?