Sometimes it just happens. At this point you just need to figure out which part is defective. Could be the computer's video card, could be the stupid cable, could be the monitor. If you're going to take the monitor home with you, you might as well take the cable as well so you can test that. If you connect it to your PC with the existing cable and it works, then you know the monitor and the cable are fine If you connect it to your PC with the existing cable and it doesn't work, swap the cable, and if that doesn't work, then you know it's the monitor.
-What is best in life? -To crush your enemies, see them driven before you, and to hear the lamentation of the women.
The problem is with "no signal" is that it can be almost any problem. If the computer turns on but doesn't successfully POST ( video card, motherboard, memory, cpu, psu ) then it will say no signal, because the computer is on but the display isn't receiving a signal. People always think it is GPU/display related, but it can be anything. If the motherboard is bad but it a least turns on, it can do this. Even a bad memory stick can cause this.
So in essence, it can be anything. Just don't limit what you check. In all honestly the whole computer can be screwed at this point. Hard to pinpoint. Does the computer normally have a POST beep? Usually a successful POST will have a single beep.
You can spend $400 on a console and $400 on a cheap PC, or you can spend $800 to build your own and have the best of both worlds.