Your biggest problem is that new video cards require UEFI in the motherboard instead of a Legacy/standard BIOS. HP didn't begin using UEFI until mid-October, 2012. The motherboard can't be upgraded to UEFI. The last cards not to require UEFI were the GTX 660/670 series. Also, you will have to upgrade the power supply unit (PSU). The existing PSU is only 250W. New video cards require a PSU of at least 400W. I normally recommend at least 500W. I like Corsair products.
Please click the Thumbs up + button if I have helped you and click Accept as Solution if your problem is solved.
I am not an HP Employee!!
Intelligence is God given. Wisdom is the sum of our mistakes!!