I just built a new computer, first time it booted it up it worked fine but my RAM hadn't arrived and so I used my friend's RAM. I accidentally knocked over my computer, when my RAM arrived I put it in and my computer seems to start up fine....fans start spinning, lights come on and stuff like that but no matter what type of cable I use the monitor just comes up with 'unable to detect source'. I know the monitor is fine because I plugged the monitor into my laptop and it works within a couple of seconds