Bought New GPU, Computer Won't Boot Past First Screen

[Herp_Derpson]

Recently, I bought a GTX 960 from MSI to replace my old GTX 650 Ti. When I installed the card in my computer, it refused to boot past the first screen that pops up when the computer starts. It beeped 3 times, with about 20 seconds between each beep, and after the third beep it goes to the black screen with the blinking underscore. I can get the computer to boot normally with integrated graphics, and the PSU and motherboard were both playing nicely with the old card just hours before trying to install the new card.

Solutions I have tried:
Clearing the old Nvidia Driver
Resetting the CMOS on the motherboard
Using the six pin to 8 pin adapter included instead of using an 8 pin connector on my PSU
Trying to reinstall an Nvidia driver before installing the card
Attempting to boot into safe mode
Swapping out the first card with another one

Yet nothing has worked. Does anyone know what is going on or how to fix it?

Computer Model: Gateway DX4870-UR11P
OS: Windows 7 Home Premium SP1
CPU: Intel Core i7 3770
PSU: Corsair CX600 (600W)
BIOS: American Megatrends

 

[shivababbli]

just remove your hdd and reconnect

 

[Herp_Derpson]

How exactly would that help?

 

[shivababbli]

just try once. coz due to hdd failure sometimes you will get a black screen with a blinking underscore on the top leftside of screen