Constant flickering on switch on after downloading Windows 10

Hello, Hope someone can help me. After getting the Windows 10 "Upgrade" window, I continued with the upgrade as directed. On completion when my screen finally came on it just continued to flash and the icons in the bottom of the screen never came on. That's where the clock is Wi-Fi icon, battery shows up etc. The I got a Runtime Error saying "Program:c\WINDOWS\system32\atibtmon.exe". I am at a total loss and not being computer savvy I really need please. Thanks