Why wont my monitor come on after the first reboot for installing Windows 10?!

[Windows Central Question]

Hi can anyone please help me, i upgraded from windows 8.1 to 10, it did its thing of gathering the files then it said it had to reboot, and after that the computer is coming on but the monitor is getting no signal! i even went and got an old monitor and its doin the same thing saying no signal, i have and nvidia graphics card installed, so im wondering in thats the problem. should i put the old one back in and restart? its an amd card that came with it. i had made a windows 8.1 restore disc before hand and tried to use that to fix it but the monitor still wont come on so i dont know if that is working or not either. i really hope i didnt just brick my pc for this stupid update.