GTX 780 not compadeble??!

[afellowgamer123]

hello guys!
i got my hands on a zotac gtx 780 3gb
i bought a 750w psu
and when i installed it put all the cables i nothing works!
the graphicscard fan spins and the logo lights green but i get no picture!
i went in to bios on my motherboard and dublechecked that onboaed grapics was turned off but nothing happend!
i took out the vga cable (with an adapter) from the graphics card and put it in my motherboard and then i got a picture i got in to windows went in to device maneger but i saw no graphicscard only microsoft display dirver somthing, i tryed to install the drivers from nvidias website but got an error messige that it could not find anny graphicscard! Please reply i dont want 400$ to go to waste. BTW i cant leave in the graphics card back to the shop!
srry for bad english
specs:

120 gb kingston ssd
500gb HDD
motherboard:fm2a78m-dg3+ (newest bios)
cpu:a6-6400k
old graphicscard:gtx 560 se 1 gb
new:gtx 780 3 gb zotac
usb wireless adapter
2 gb ram (getting 8gb in like 2 days)
case fractal design core 1000 (m-atx)
sys: windows 8.1 pro 64 bit

 

[Yoann Teodosieff]

The only thing i get in my head is that you did not push it to get it into the slot. When you connect to the motherboards port then the motherboard doesnt recognise that on it is a GPU. But thats not important, too because you will see huge bottleneck when you try to play games.

 

[Whtwolf]

Have you pulled it out, and reseated it?

Does your old card work in the same slot, and do you have the extra power hooked up to the card?

 

[afellowgamer123]

Have you pulled it out, and reseated it?

Does your old card work in the same slot, and do you have the extra power hooked up to the card?

yes my old card worked!
i took out the new one and reseated it multiple times
btf when i inserted it and diddent connect anny power cables the card logo was glowing anyway could it be that i got a faulty psu , but the first card worked just fine!

 

[afellowgamer123]

btw i have returned the psu so if i connect it to my current 500w psu will i like show bios screen at idle
its not 80+ certified