Questions on setting up RAID controller

I bought an Abit KR7A-RAID in January and I'm waiting on the arrival of WinXP to install. Right now, I've got two hard drives hooked up to the mobo on "regular" connections, one acting as the master and the other acting as the slave. The master has the OS on it and the slave is used to store games, data, etc. What I would like to do when I do a clean install of WinXP is set up the master HD with the OS on a RAID device. Here's a few questions:

1) Do I have to have at least 2 HDs to set up a RAID array or can I just do the one? I don't have a back-up device that I can transfer my "slave" HD files to.
2) If I have to have 2 HDs, there's something in the mobo User's Manual that says the HDs should be the same brand and model. Well, my two are different brands, so will the RAID controller really buy me increased performance?
3) I'm not too familiar with the jargon in the User's Manual, either. What kind of array should I be setting up...Striping (RAID 0), Mirror (RAID 1), or Striping + Mirror (RAID 0+1)?

Mucho thanks in advance.

Yes you need 2 drives, at least 2.

They don't have to be the same but it is best, performance wise, if they are.

For performance you need to set up RAID 0. RAID 1 is simply a backup setup. RAID 0 + 1 will give you both but you'll need at least 4 HDDs.