Welcome to TS. Our forum for Guides & Solved Issues is helpful in situations as this one. This forum will help you understand this problem in ways that many here can relate to.
Here is what I think I know. The power supply received the Go signal from the mobo. The fans are running & some LEDs are flashing. You have not called attention to any beeps, meaning the mobo passed the POST.
The only symptom that you have related is No Video. What other symptoms are being presented? Is there no hard drive activity?
No video is a big limitation. Test the monitor with another computer.
More details / symptoms will give everyone better insight into you problem.
Don't boot means many things to different people. In a healthy system, new hardware / software causes grief. In older systems, things just wear out.