Hit CTRL-ALT Delete while it is in that state, can you get to the Task Manager?
If you can, then it is possible that your activation has failed. This happens sometimes. To fix it, you have to do an "In-Place Install" - Stick your Windows 8 Install disk into the drive and browse to "Setup.exe" on the disk from task manager.
If you have no task manager, then you may have errors on your disk. Windows 8 cannot fix read element errors, you have to run an external disk scanner. There is a link to Hiren's Boot CD below my Sig picture, cloisk on that and download it, burn it, and boot from it - Look for 'Dos Programs" and choose "Hard Disk Tools" - Look for a program called "Vivex" or something similar.
Within that program there is a "Smart Remap" function - Just run that, skip all of the preliminaries, see if there are any disk errors. THIS WILL TAKE up to 2 hours - Go somewhere and come back after that time. It will show you the fixed areas.
If it finds errors and fixes them, reboot to Hiren's and then run "Mini XP" - and run a full CHKDSK c: /x /r from there. After that is done, reboot and see if Windows 8 finalizes any Auto Repair that may have been scheduled.
