I hope this is a simple question, but I simply don't know anything about RAID.

Some time ago I received a machine that, as I understand it, has two drives in it under RAID 1 (or so that one drive is mirrored on the other and appears as just 1 drive to the OS). Recently, one of these drives has started marking a clicking noise and I would like to replace it. I believe the machine has a hardware RAID controller on the motherboard that handles the RAID stuff, but if it matters the Operating System is Windows XP 32-bit.

Is the solution to my problem as simple as buying another drive that is of the same capacity and plugging it in where the clicking drive is currently? Or could I possibly lose everything if the drive that's clicking is the one being mirrored on to the other drive? Is there some menu I need to find before unhooking things? Any best practices out there?

I'm sure I'm leaving out some required information, so please just tell me what I'm missing.

Thanks!