Right so I built another computer using some old spare parts, and I got it running just fine. But when I installed the same HD that I was using in my damaged computer, I got the same problem again. No signal, no beep. And it doesn't matter if I disconnect the HD again. It still wont boot.
So I'm thinking the most probable cause is ; my HD must be infected with CIH or something. That's the only virus I know of that can wipe out BIOS. That would also explain why my computer crashed right after I installed and ran the new software I found on the internet.
I'll let you know what happens, I'm gonna order a new BIOS ship this week.