Best way to mirror 2 1TB SATA HDD's

I built a PC a couple years ago around an Asus P5B Deluxe mobo. The machine is dual boot, with XP Home on one 320 gig HDD & XP Pro on another. In addition to that, the PC has 2 500 gig hdd's, and I recently added 2 1TB drives, for a total of 6. All are SATA. I use the PC mostly for web access & as a HTPC.

My question relates to setting up the 2 1TB drives, which I plan to use as storage only, so that they mirror one another. I have attempted to set them up in a RAID 1 configuration, without success. The mobo has the Intel ICH8R Southbridge RAID controller, as well as (apparently) a JMicron JMB36X RAID controller. Following the instructions in the mobo manual, I set the BIOS SATA config to RAID, then went into the Intel Matrix Storage Manager & selected/config'd the 2 drives in question as RAID 1. After this, neither OS would boot (goes through post, flashes a blue screen too quickly read, then repeats). I had to go back into BIOS & reset the BIOS SATA config to IDE in order to get into an OS. I'm guessing that, since BIOS has no option to set 2 HDD's as RAID and the others as IDE, selecting RAID globally blocks the 2 OS drives from booting.

Oddly, even after resetting the RAIDed drives to non-RAID in Southbridge, when viewed in WD Data Lifeguard Diagnostics, only the 2 new 1TB drives are listed as SATA, the other 4 are listed as IDE. Not sure of the significance of this, if any.

So, is there a way to implement RAID 1 on just 2 of my 6 drives, and have it function across BOTH OS's? If not, is there some other way I might accomplish the same goal?

Thanks in advance,

Dan