I want to know how to set up a Raid 0 system

I have an Asus P5B motherboard that I want to set up two 250 gig Sata drives into a Raid 0 configuration on. My problem is that I can't seem to find a description of how I am supposed to do that. I believed that I was supposed to plug one Sata drive into the Raid Controller, and plug the other drive into the the Sata 1 port. I went into the bios and made sure the Hard drives and the controller are enabled and set for Raid mode. I made up a floppy disk with the Asus Jmicron Raid files (drivers) and went to install my OS, which is XP professional 32 bit. I pressed the F6 button and selected my JMicron Raid driver to load into the Xp installation.

When the windows installation program loads, it asks me where to install windows. It shows that I can install it on one of my hard drives (listed as a Jmicron by XP), but I notice that the size of the drive is 250 gigs, instead of 500 gigs that I had figured it would show if it was a Raid 0 configuration. Obviously something is amiss.

I don't even know where I was even supposed to say how to set the drives up for RAID (0,1, 0+1, 5, etc). Since I don't know exactly what was supposed to happen, it is kind of tough for me to identify the problem.

There is also a Jmicron program that is built into the motherboards Bios that I can Run by pressing ctrl-J. It shows one 250 gig hard drive (listed as non-raid). I try to press the create raid array option, but it gives me an error message saying "Error, not enough disk", which isn't even proper english, so I don't really know what it is trying to tell me.

Can anyone drop a clue my way as to what I am supposed to do to make this work? Thanks in advance.

From Asus' site

P5B
Storage

Southbridge
- 4 x SATA 3.0 Gb/s ports
JMicron® JMB363 PATA and SATA controller
- 1 x UltraDMA 133/100/66 for up to 2 PATA devices
- 1 x Internal SATA 3.0 Gb/s port
- 1 x External SATA 3.0 Gb/s port (SATA On-the-Go)
- Support SATA RAID 0, 1 and JBOD (by 1x External SATA & 1x Internal SATA)


So does this mean it will only work with the External Sata and the Internal Sata, that would suck.