The short solution:
1. Find another PC/notebook using Windows 8 system
2. Create a USB recovery drive from that computer
3. Boot from the USB drive and enter the Windows 8 advanced startup menu
4. Troubleshoot -> Advanced Options -> Automatic Repair
Links:
http://pcsupport.about.com/od/repair-recovery/a/recovery-drive-windows-8.htm
http://pcsupport.about.com/od/windows-8/a/open-advanced-startup-options-windows-8.htm
http://www.techrepublic.com/blog/windows-and-office/create-a-recovery-drive-in-windows-8/
http://www.youtube.com/watch?v=6v5ewszMtGQ&list=PLaMGK8uBGSYvKc60rA99X-Z90N5cWF72M&index=21
www.tekrevue.com/tip/how-to-scan-fix-hard-drives-with-chkdsk-in-windows-8/
http://pcsupport.about.com/od/tipstricks/ht/bootusbflash.htm
http://www.tomshardware.com/answers/id-1726133/preparing-automatic-repair-black-screen-error-loop.html
http://answers.microsoft.com/en-us/windows/forum/windows_8-system/windows-8-stuck-in-endless-preparing-automatic/82d41567-fe16-4c32-b3f0-5a202b4ef16b?page=3
http://windows.microsoft.com/en-us/windows-8/create-usb-recovery-drive
