It happens to the best of us. We spend hours putting together a new PC, mounting a nice aftermarket heatsink, making sure all the cables are nicely organized, and we're just so glad to get Windows installed that we forget one detail: setting the storage controller to AHCI or RAID mode. Both settings enable native command queuing, which can improve performance, but switching settings after loading up Windows almost guarantees a nasty bluescreen.
I had enough foresight to enable AHCI before installing Windows last time, but I stayed clear from the RAID setting. That came back to bite me in the butt last weekend, when I received a fresh Western Digital Caviar Green 1TB hard drive in the mail and decided to arrange my dual Caviar SE16 320GB drives in a RAID 1 array. For the uninitiated, RAID 1 essentially mirrors the contents of one drive onto another drive. That doesn't remove the need for backups, but if applied to an OS drive, it can save quite a bit of time in the event of a hard drive failure.
Microsoft provides simple instructions on switching from IDE to AHCI mode, but switching from AHCI to RAID was another story—at least on my Intel P965 Express- and ICH8R-powered system. I still got the bluescreen at boot-up, and no amount of Googling or tinkering with drivers solved that problem.
Finally, I found an easy solution. My motherboard has six Serial ATA ports running off the ICH8R south bridge, and a seventh SATA port is hooked up to a JMicron controller. All I had to do was connect my primary hard drive to that controller, make sure it was in IDE mode (since Windows has built-in drivers for that), and set the Intel controller to RAID mode. Vista happily booted off the JMicron and recognized the "new" Intel RAID controller my other drives were hooked up to, allowing me to go back, connect the OS drive to the ICH8R again, and finally boot with the RAID setting enabled (and no hiccups).
Wasn't this all for nothing, though? Wouldn't building a RAID 1 array from there on involve reinstalling the operating system anyway? I'm not familiar with other storage controllers, but Intel's handy Matrix Storage Console software allows you to skip that step and create a RAID from an existing boot drive. Somehow, it doesn't care if there's an OS installed on it, and you can keep running software and doing whatever you need to do while the conversion process goes on in the background. Neat.
After about six hours, my dual 320GB Caviars were joined in holy redundancy at last, and I finally went to bed. Somehow, though, Windows wasn't happy the next time I rebooted, since it asked me to re-activate it—and the online process didn't work, so I had to use the gruelling automated phone system, juggling groups of digits and confirming that, yes, my operating system was still installed on just a single computer. That may have been the most annoying part of this whole endeavor, actually.