PC boots ; No monitor signal - Please help

OK, SO, basically my PC is booting without signal being received by my monitor.. i don't have a pc speaker so i can't hear the bios, but i can hear it launch windows (i can even log in, and here it do so) .. yet my screen remains black.

This problem ensued after i opened my PC up to put my laptop hard drive into it.. In the process, i wiped some dust from the top of the graphics card with my finger (i wasn't static'y), i also may have been a little aggressive with the MOBO in attaching the SATA cable but honestly I don't feel i did anything to provake damage...
Once i had plugged the harddrive in, it sort of hung awkwardly upon the graphics card (yes metal touched metal) but again, im not sure this was of any significance - ofcourse im no expert so my judgement on all of this is probably way off.

I've covered all the basics... Tried a different monitor, different DVI cable, took out the graphics card multiple times and resat it, tried puting it in the other MOBO slot, made sure all cables were secure...


I really am at a loss about this and incredibly upset at the prospect of no PC access for the foreseeable future.

TL;DR - No monitor signal but can hear WIN7 audio on boot up - Tried to attach additional harddrive, may have caused damage to graphics card/mobo whilst dusting/pushing cables about.

ALL ADVICE WELCOME.