Help with RAID PLEASEEEE!!

[shahzafar]

My system Specs:
Intel Celeron 1.2GHz with 256MB RAM
40GB ATA HDD
250GB external USB drive.

I installed ubuntu 6.06 server on the 40GB HDD and I selected option 2 while installing which partitioned my drive and installed ubuntu on one and the other is available for data storage. I was also able to mount the 250GB external HDD.
Now, I bought an Adaptec 1210SA RAID controller and two 250GB SATA drives and am trying to setup RAID1 with them. I used the Adaptec BIOS utility and configured RAID1 on it. Now, when I boot into the kernel, it recognizes the disks(new 250 GB SATA) and shows two disks individually. Should I mount both of them? Should I use dmraid and configure the RAID1 again? Can I setup RAID1 in my present scenario? With the 40GB primary drive, 250GB external HDD and these 2 new HDD's?
I am new to all this, so please try to help me.
I read a lot of posts about configuring RAID on ubuntu, but all of them talk about configuring new system and installing ubuntu to the RAID. I already have a server running and want to add two more disks to it in RAID1 configuration. Can this be done? Should I just have the two 250GB SATA drives and remove all other drives? Please help!!!!

I am just using this as a NAS for my home.
Thanking you in advance,
Zafar.