I had the same problem. I set the XD bit to 'enabled' in the BIOS setup and it worked. Unlike the posts on the internet, the XD bit is displayed either in the BIOS tab or ADVANCED tab.
Steps: Boot your PC into setup BIOS mode by pressing the 'Delete' key continuously during boot.
When in BIOS settings, search for the XD flag either in BIOS or ADVANCED tab. If you can find it, then search it in all other tabs.This depends pn PC manufacturer and can be located in any other tab.
Set the XD flag to 'Enabled' and you are done.
Boot the PC and you are ready to install Windows 8.
Let me know if you need some more info.