Just bought a new computer,(out of box) and i turns on (lights+fans) i get 1 beep but nothing shows up on my monitor. Ive tried two different monitors same problem with both, but they work fine on the other computers.
Go to store get replacement from where you bought it
Agreed; sounds like a bad/defective computer (happens sometimes). Basically, if it's a system someone else made for you, don't try to fix any hardware yourself, just take it back and exchange it for another of the same model.
The only time you would try diagnosing hardware problems is if it was out of warranty or you built it yourself.