Just a few questions first, to understand the issue better:
1)Did you use the Upgrade assistant to install Windows 8? Did the Upgrade assistant find any devices or parts of the computer to be incompatible?
2)What is the make and model of the computer?
3)Do you have a Windows 8 installation disk?
Since the computer doesn’t boot after the Windows logo, I would suggest you to try these steps and check:
I would first suggest you to remove all external devices connected to the computer except essential devices like keyboard and mouse and then boot the computer and check.
Method 2: Automatic repair
If you are unable to boot the computer, then I would suggest you to perform an Automatic repair. The Automatic repair can detect and fix the issues that prevent the computer from starting normally. You will need the Windows 8 disc to
perform an Automatic repair. Since you upgraded through upgrade assistant and don’t have a Windows 8 disc, I would suggest you to download Windows 8 from another computer through this link and choose to create an installation media when the upgrade assistant