This is a tough one since I don't know what MOBO you are using, your BIOS, or the RAID controller. I assume the RAID list you are talking about is the RAID setup menu and not a list in your BIOS. The last time I did this here is what I did...
first I made a driver floppy disk with the SATA RAID drivers on it using my other computer.
next I hooked up both drives into SATA ports 1 and 2 of my MOBO (since I used onboard rather than an add-on controller card)
I then went into my BIOS and made sure it saw both drives, then I activated SATA RAID in the BIOS. (I think it was automatically set up for SATA ports 1 & 2) next I set the boot priority to <1. CD <2. harddrive (with the HD setting for scsi raid)
then I saved changes and exited BIOS.
After that I went into the RAID menu and my system saw both the drives so I set up a bootable raid 0 and saved the settings
then I let my system run with the windows CD in the drive and it started going through the set-up. almost right after the blue screen comes up it says <press F2 to install 3rd party scsi raid drivers> which I did. after a while a window pops up and tells you to insert the disk (floppy) and it will have you load the drivers manually from a list that pops up in the window. My disk had 2 different drivers on it and both needed to be installed. after that I just let the whole install process run and everything went fine.
I was using an ASUS A8N-E MOBO and 2 74gig raptor drives. The raid drivers I used were on my MOBO CD and my OS was XP pro.
I recently tried it again with XP64 (I downloaded the 64 bit raid drivers and made the disk) but it would always have problems loading the raid drivers and I couldn't get it to work.
anyway I hope this helps some even though I really have no clue why your RAID menu isn't seeing both drives...
CT