My PC's Windows 8 partition got destroyed. How can I fix it?

I had a nice setup with my desktop PC running Windows 8. It had been running fine since the first or second of this month - when I installed it.

But after attaching my laptop's HDD with a SATA cable and unplugging it again, I got a message to restart because of drive errors.

So, I restarted. Windows rebooted itself several times, and at the end, it produced a BSOD, complete with new sad face and a message: 0xc000021a. I've seen some methods online, but replacing DLLs? Seems risky to me.

Startup Repair (which started automatically) didn't fix the problem.

I can boot into Windows 7, however.

How would I fix this problem and get back my Windows 8 installation?