An HP tech had to replace my motherboard (twice within a short period, actually) and now Windows 8 wants me to reactivate. I get this error when I try to go through the activation process:

What do I do?
Update: I got this output when I ran the first command in magicandre1981's post.
Deployment Image Servicing and Management tool
Version: 6.2.9200.16384
Image Version: 6.2.9200.16384
[==========================100.0%==========================]
Error: 1392
The file or directory is corrupted and unreadable.
The DISM log file can be found at C:\Windows\Logs\DISM\dism.log
I also called Microsoft tech support and I gave them my key and the error code, but they directed me towards the DreamSpark site because I'm using a DreamSpark Premium key. I don't know if either of these two actions did anything to resolve the problem, but a few hours later my Windows install had been activated successfully in the background.
This notification showed up in my Action Center, but I don't know if it is related to my problems at all:

Following this notification I rebooted my machine as instructed and everything seems to work fine now. I'm not sure who to credit for solving this question, though.