In my (computer ;-) case it's RAID 1 to be exact. RAID, when used as an abbreviation in the world of computer electronics, means Redundant Array of Inexpensive Disks and there are a couple of ways of implementing and using this feature. RAID 0 This configuration is the fastest of all the RAID levels, it uses a technique called data striping (see below) and requires at least 2 hard disks. RAID 1 This level uses a pair of hard disks at a time to provide fault tolerance (there is no performance benefit) and requires at least 2 hard disks. Using a technique called disk mirroring (see below) the same data is written to both disks at a time, so if one hard disk crashes then the same data is available from the remaining hard disk. RAID 2 The RAID 2 configuration uses data striping (see below) and a fault tolerance technique called parity (see below), it requires at least 3 disks. Two (or more) of the disks are used to store the data and one disk is used to store the parity (see below) information. RAID 2 strips the data into bits which is why RAID 3 (below) is a better implementation as it strips the data into bytes instead. RAID 3 A common RAID level similar to RAID 2 except that the data is striped into bytes and not bits, giving a performance benefit over RAID 2. RAID 4 RAID 4 strips the data into blocks and uses a parity drive for fault tolerance, at least 3 drives are required, not a commonly used implementation. RAID 5 A popular RAID configuration utilizing at least 3 drives. Data is striped across the drives in bytes, the parity data for one particular drive is stored on another drive allowing the data to be rebuilt using the parity technique. Since I'm on a bit of a tight budget but wanted a fault tolerance system RAID 1 was the way to go for me. So I got myself two 250GB 7200RPM 16MB cache SATA150 drives and set them up in a RAID 1 configuration in my PC's bios. Then I encountered another problem: Windows needed to know what controller it should activate as at that point the setup didn't recognize the correct controller. Now I knew I had to have a floppy disk somewhere with those drivers on it but finding it was going to be a bit of a problem. Luckily for me Bas took my advice on which motherboard to buy and because we bought our upgrades at the same time we now have the very same basic configuration and therefore also the same motherboard. So I asked him to look up the floppy because I know that a) he's a bit more organized than I am and b) he only has about 5 floppy's so it should be pretty easy to find it. Specially when compared to me, because I would have had to go through piles of floppy's and CD's to find it. When I got the disk from him the Windows setup could continue and was finished about 20 minutes later. And that's the state things are in right now. Tonight I'm going to see what data can be restored from the other drive so I can hopefully finish the whole business up this weekend.