Reseat the graphics card. Check for loose power connections. Just because you havent touched anything doesnt mean they may not have just come loose on their own! Also, it seems rare for a graphics card to just die without warning like that (usually you get artifacting or something odd first) so maybe move the GPU to another graphics slot on your board. 
 
To answer the 2nd part of your question, no. If you bought a GTX 780 SC and put your own water block on it... You will have to return it to its original state prior to shipping it to EVGA. They do not want your 3rd party cooler, nor would you get it back necessarily. Now if you bought a GTX 780 that came with the waterblock/backplate on it, then it is already "stock" and can be replaced as-is. 

houkom
Reseat the graphics card. Check for loose power connections. Just because you havent touched anything doesnt mean they may not have just come loose on their own! Also, it seems rare for a graphics card to just die without warning like that (usually you get artifacting or something odd first) so maybe move the GPU to another graphics slot on your board. 
 
To answer the 2nd part of your question, no. If you bought a GTX 780 SC and put your own water block on it... You will have to return it to its original state prior to shipping it to EVGA. They do not want your 3rd party cooler, nor would you get it back necessarily. Now if you bought a GTX 780 that came with the waterblock/backplate on it, then it is already "stock" and can be replaced as-is. 

Thanks for the info..
I have the standard GTX 780 (2781) so it had the reference-cooler. Good to know that i have to put that one back if i should RMA it. Thank god i kept it :) 
It seems that it was not actually dead lol.. tho it was weird that is was "lost" in the device manager.. Because the HDMI-port appear broken. I tried with a DVI-cable and it works fine.
 



 

rcarlos243
does you fan spin at all?
also does your computer turn on then off after a few seconds?
could be your PSU or maybe the VRM on the GPU has failed.

I dont use the fan :)

Graphics are not dead (GFX stand for graphics or graphic effects) but like houkom said, check your connections and make sure everything is seated. It may also be the PCI lane acting up, so you may want to break down the loop and try installing it in another lane before assuming 100% it is the GPU.

There is "question about GFX" thread going. You should take look at it. It's comical and may make sense about the first part of my post :-P lol.

Generally, if the onboard video is used to boot, the card will show up as not being recognized or unusable.  That can lead to an inference that the card is bad.  However, it seems your testing shows that it just may be a bad HDMI port.  You are free to keep using it on another port, but if the card is still under warranty, EVGA will replace the card for you if it has a bad port.