add more hard drives

[Ayman Altounji]

Greetings,
Here is a spec of my compaq DL380 server:
cpu: (1) 733Mhz
ram: 1.5Gb
HDDs: (3) U3 hot-plug
raid controller: (1) smart array 431
OS: win2k adv. server w/ active directory, dns, and dhcp services running.
-current configuration-
1. disk0 and disk1 are mirror (Win2k OS resides here)
2. disk2 is stripped- raid 0 (DATA resides here- folder redirector, home)
3. Win2k disk manager utility show all dirves as "Basic Disks" for drive C and D.
-want to upgrade and final result-
1. What is the path or procedure if I want to upgrade the data volume to 18Gb and have it mirror for fault-tolerant?
2. How do I go about populating the second cpu and have win2k recognize and utilize them both?
Please help..