Can anyone point me in the right direction??

i have an eee pc 900 (20g) i have windows installed on my 4g primary and i want to put BackTrack 3 on my 16g secondary drive and be able to choose which OS to load when i turn my eee on.

has anyone done this yet on there eee? i found loads of information on installing BT but i can't figure out how to set it up for two seprate drives.

any help with this would be greatful