This usually points to a corrupted system registry. Do you have a Live CD such as Knoppix you can boot from and look to see if there's a registry backup?
If you cannot create a bootable CD, can you access a command prompt from the advanced options?
Usually registry backups are located at C:\windows\system32\config\RegBack
You can attempt to copy these files into your system32\config folder, and overwrite the old corrupt ones (MAKE A BACKUP OF THEM FIRST).
This may get you able to boot.