My understanding is that one can't simply add a second HDD to a raid 0 array that's already going. I've been under the impression that you need to set the whole array up at the same time and hope nothing fucks itself. RAID 0 specifically. It at the very least requires reinitializing the array and reloading the RAID and ACHI drivers.
There was no raid array to begin with, just a single HDD. I was adding a second drive in order to create an array. All the system image restorations were also to the array, not individual drives.
Ether way, I got it working by loading drivers during the recovery process on DVD (using the load drivers button that is supposed to be used if the recovery console can't see the drives). As it turns out, windows 7 since day one thought it was installed on bog standard IDE hard disks, so the presence of RAID/ACHI made it freak out and quit. If it had installed the correct drivers when the OS was originally installed, non of this would've happened. But hey, that's windows for you!
Shot in the dark, something about the RAID is messing with permissions? I don't know anything about setting up RAID but if I saw a message that said something like "crash dump initialization failed" my first guess would be to find out why it didn't have permission to proceed.
No permission errors. I did another restore from the system image to the RAID array but this time loaded some ACHI and RAID drivers using the "Load Drivers" button in the Win7 system recovery on the DVD. Its meant to be used when the recovery console can't see the disks you want to restore too.
The system took forever and a day to boot once the restore was complete - but after the first boot it installed the ACHI and RAID drivers I loaded and has been running like a champ since then.