I recentley bought a GTX 550 Ti hoping to use it in my HP computer. I installed it in my PC, and I am pretty sure everything is connected properly. The 6-pin power connecter is plugged in. Windows will not recognize it, and my HP bios does not have any option to disable onboard graphics.
Specs: HP p6-2110 ASUS GTX 550 Ti Intel Pentium G640 2.8 GHz Corsair CX430 8gb Crucial Ballistix 1TB HDD
More aboutgiving signal
Maybe , this could help. Try removing the card and inserting it once again.