RAID setup with a new hdd and a used hdd plz help

[masterg]

i have a WD 160gb cavier on my original build; unfortunately, i hit the its max very fast. i just now bought a WD 400gb cavier but i do not know how to set these up so that the info on my main drive will not be lost;

when i setup my RAID it says all stored info will be lost

please help

[zanzabar]

u need identical drives to raid just run them on ide mode

[masterg]

i run them on auto ide and i start up my pc and my desktop says found new hardware 400gb hdd, ready to use

but on my computer the drive does not show up

and my first drive does not show signs of increased size

[masterg]

if it helps any, it is a wd 400gb cavier hooked up to sata II on a dfi infinity 975x using award bios 8.0 i believe

[zanzabar]

go to admin tools/computer management in the control panel (classic view)

then storage/disk management and format the drive

[masterg]

thank you