Thanks for the reply wiganken but I solved the problem. I had to replace the vga cable with another one and it worked. It's a bit strange though but it works now.
BTW, it's Intel integrated graphics, might be a driver problem.
So I was trying to install Windows 8 64 bit on my PC (which already has windows 10 as main OS) but from some reason whenever I try to boot from the bootable USB, it shows the windows logo and then the screen goes black with a massage saying that the input timing is not suppoted. The max...