No Screen signal when I turn on my PC

Hello,


Yesterday, my PC was running smoothly, I wanted to install my recovery HDD (Which contain files that I don't want to loose). I turned off the PC, took all the cables off, placed the HDD in the HDD box inside my PC case, re put everything back and started the PC. I got 3 long Beep messages (which refer to the RAM) so I switched my RAM slots and turned back the PC on, there was no Beeps, everything is running, I can hear the fans running, HDDs doing the normal sound but there is no signal on the screen (note that the HDD led lights when I first run the PC and then it stop lighting). This issue happened to me before, I took off the CMOS and replaced it (as it solved my porblem before) but there still no signal. I tried plugging in the DVD Drive (It was always plugged off as it keeps getting in and out so I unplugged it) but there still no signal on screen.

Finally, I took off the new HDD that i placed and still no signal on screen.


Please, any help would be much appreciated!

Cheers,

Hassen B



Edit:
- If this helps: I don't really think that the Motherboard is dead as the PC was running normally.
- PC Specs: Intel Core 2 Quad Q8200 2.33Ghz. 3GB (2GB + 1GB) DDR2 RAM. Gainward GTX 550Ti GS Graphic Card, OCZ 550W Power Supply, WD Caviar Blue 640GB (The System Hard Drive) and Segate Baracuda 500GB (The HDD that I tried to install).