MSI Graphics card not working on both modes.

So i bought the MSI Nvidia Geforce GTX 750 TI OC Gaming Edition graphics card as an upgrade from my old Asus Radeon HD 6670 and everytime i've tried replacing it, it goes to the blue HP welcome screen, beeps 3 times then switches to a black screen with a flashing underscore, here's what i've tried:
- Clearing the CMOS (Taking the battery out of the motherboard for half an hour).
- Re-Fitting the card.
- Switching to Legacy BIOS and Hybrid BIOS (Neither works)
- I Used a program to remove my old drivers before installing the card to prevent conflicts.

What i know isn't the problem:
- My PSU is 450 w, this card requires only 400 and there is no socket in the card, it runs off the graphics card slot power.
- My old graphics card still works perfectly so i know the slot isn't broken.

Anyone know what i can do to fix the issue? I know it certainly is compatible with my pc.