Bad luck, you say? Sometimes, there's no other alternative.
Not the silvered looking-glass devices you non-geeks are accustomed to. I'm referring to drive arrays. The 800-pound gorilla that is my terabyte data store needs to be re-done...that means backing up all the information to another drive (or 4), killing the existing RAID, making the new mirror (because all of this is destructive to data), and restoring the 900+ gigs of 1's and 0's. So much fun for so much pr0n.
While I'm on this thread, I should say that RAID arrays *ARE* effective as a full-time backup solution. Hard drives keep getting larger AND cheaper and one terabyte SATA at $70 or less is plenty of storage, even for me. If your platters are spinning 24/7 (as mine are), the chances of a disk going bad increase - so save your precious bits with redundant technology.
Wanna know my partitioning scheme? Check this out:
Drive 0: 80 GB SATA
40 GB C:\ this is for the Operating System only. Do not save your personal data here. When it dies (and it will), your data will not go with it. Keep this small, uncluttered, and defragmented for performance and management reasons.
40 GB D:\ this is for applications. Install all your software here. When you run setup.exe for whatever software you're loading, it'll give you the choice of where to install: Instead of c:\program files\blahblahblah, switch it to d:\blahblahblah. Located on the same spindle as the OS for performance
Drive 1: 1000 GB RAID-1 set
1000 GB X:\ This is where your personal data goes: music, videos, pictures, everything I don't want lost. I also keep copies of my installation media for all my applications here. When drive 0 goes bad, replace with a new drive 0 and a fresh install of windows and applications.
..and yes, you can mirror your OS, but I just don't see the value of having redundant OS files. The space is better used for my pr0nz.