When I switch on my computer, its starts but my monitor stays black and muy computer gives me 3 beeps and stays on but inactive. I don't know if the problem is the computer or the monitor (The monitor is on but with the orange light instead of the green light). Someone help me please? :(

Check out the beep codes at Techrepublic... Specific beep codes depends on the BIOS and PC manufacturer.

http://techrepublic.com.com/5100-1035_11-1043759.html?tag=search#

Sounds like your graphics card has come loose. It should just be a case of opening up your PC and ensuring that the card is seated properly. Best thing to do would be to take the card completely out of its slots and then put it back in. You'll probably have ot be a little firm with it to make sure it's in properly.

Only open up the PC if you are confident doing so though. You can do a lot of damage to your PC and/or yourself if you don't know what you are doing.