Hi,
Atikmdag.sys is the ATI driver. Updating the ATI drivers or reinstall the present ones may fix the issue.
As you are able to boot to Safe Mode, I would suggest you to perform system restore in the safe mode to the date before Windows Updates were installed.
Refer to “Restoring your PC to an earlier point in time” from the link below:
http://windows.microsoft.com/en-gb/windows-8/restore-refresh-reset-pc
After performing system restore check if you can boot to the desktop. If yes, uninstall ATI Radeon graphics driver and install the latest driver from manufacture website. Later you can perform Windows Updates and check if the issue persists.
Let us know the status of the issue. If you need further assistance, please post back. We will be glad to help you.