How did you install Win 8 to start with? If this was an upgrade from the download, you might need to start over. Can you access the email receipt you received from MS? If so there is a link near the top to start over. I would follow this and choose the Install from Media you create option, burn a DVD or Flash drive and start over. Boot to the Media and do a Custom Install.
Many of these very strange failures are caused by the Upgrade Install going bad.
I always recommend 2 things:
1) Always create the installation media from the ISO download. This gives access to the Repair Console through Repair my computer on the DVD
2) Always do a Custom Install, not an Upgrade Install. In my case I use the Disk Options (Advanced) link and...