No video on dell precision 330??

[Eighty8lx50]

I sprayed out one of my pc's with compressed air to get all the dust out and now the computer has no video, I start it up and it sounds like its starting up but no picture. I tryed changing video cards and that did nothing. What could be wrong?

 

[Eighty8lx50]

I got it, It was a memory stick that was not installed all the way in the socket. My friend was messing with it last night and did not put it back in right.