No Signal...

Please I need help, my PC doesn't display anything... So i've had my home built PC (Asus P5Q Pro, HD 4870, C2D E8400, 4GB Corsair RAM) since February(7 Months), been using it for heavy gaming and everyday usage. So today I got Resident evil 5 and thought that I could connect my Pc to my HDTV, so I move my PC to my living room and use a DVi-HDMI adapter, I've done this before and I had worked wonderfully, but this time it didn't. Thinking it was something wrong with the TV I move my monitor next to my PC and connect it, but it didn't work either.

I was getting frustated so I moved my PC back to my desk, and connected everything like it was before, but it still didn't work. Then I put my PC on a horizontal orientation, opened it up and took out the Graphics Card, cleaned it a bit, connected evertything else back again with the PC still sitting horizontally and to my surprise it worked, I could boot to Windows 7. Happily I turned off the computer, closed it and put it where it was before(in a vertical orientation), turned it on and it stoped working again...

I tried taking out the graphics card again but now it doesn't work that way anymore...

Please I'm getting desperate, what can I do?... I don't have another Pc right now and I'm posting this from my Wii...

My build has worked fine for the last 7 months... I need to know if my VGA broke and if the warranty still aplies, or maybe it's the motherboard or I don't know...