Yep. Do you know what kind of card you have? Also what type of cord are you using? DVI, VGA, HDMI?
1. unplug ur atx completely and press the power-on button for approx. 20 seconds then start ur system. sometimes simply refreshing ur BIOS can do the trick.
2. take out ur gfx card and RAM sticks clean and re-insert. change the RAM stick DIMMs while ur'e at it.
see if it works if its not a hardware fault.
What is the ATX? And what's the best way to clean those things?
At the person who asked about the card and cable: All I know is that the card is an Nvidia, and I am using a standard VGA I think. (the one that is blue at the ends)
the ATX/CPU tower..the one in which u have all the hardware. this has happened to me once maybe twice where i was away for a week or so and my pc wasn't used at all.
the best way to clean ur RAM sticks and/or ur gfx card is to carefully take them out..hold them in one hand and just do the best to blow away all the accumulated dust on them. personally i have a very powerful 500W blower in my hand and that usually clears away even the most stubborn dirt particles. while putting the RAM sticks back in change the order in which they were in previously.
OP if the machine has an internal graphic card then use that, do not use the port next to all the other connections.
Also take out the motherboard battery and leave for 30 seconds then replace and switch on the PC again this will reset the BIOS to default settings, just incase the VGA option was set wrongly.