You have to go into your BIOS.
That's a firmware issue, not an OS one.
Really? I'm pretty sure Windows Vista Ultimate allows JBOD and RAID 1 mirroring and Windows 7 Home allows JBOD and RAID 1 while Professional and Ultimate add RAID 0 striping. Even the venerable XP offers disk spanning (JBOD).
Wong never mentioned whether he was using a discrete RAID controller (hardware) or motherboard embedded controller (firmware) or his OS (software).
To answer the question, one must know which of the three types he is using. If it is a discrete controller (LSI, Adaptec, Areca...), the method of entry into the RAID controller is different for each. Even LSI has at least 4 different methods depending upon the generation of controller so the model becomes quite important.