I have spent 2 days fighting this and I give up...calling in the heavy troops.  
 
New GT 740 SC, 4 Gig.
Installing into 4 year old HP Pavilion P7 desktop, AMD A10, 8 gig, onboard Raedon GPU w/512 meg, Win 7 home premium, AMI BIOS, PCI-e 2.0 slot, NEW EVGA 500 watt PS installed at same time, works great, fails at Fallout 4.  Time for new GPU.
 
Long story short(er):  install GT 740, system hangs at the HP startup splash screen, gives a single beep 3 times (about 10 seconds between them) then goes to black screen and sits for as long as I have patience to watch it (10+ minutes a time or two).  Keyboard just beeps at me when trying to type, so it's truly hung.
 
Long story, tried many things, many times:  
 
Installed new 500W power supply
Disabled onboard GPU driver via Device Manager
Uninstalled onboard GPU driver via Device Manager
Uninstalled all obvious ATI drivers/software from software uninstall program
tried old PCIe ATI GPU (256m or 512m) from different machine to test slot (works, plug-n-play)
tried new GT740 in old Win XP Dell machine, works (plug-n-play)
repeated several times, same result.  Fan on GPU starts slowly, system runs POST, and hangs at HP splash screen.  So I'm getting startup video, but a hard system hang.
 
No BIOS settings available for disabling onboard video.  Installing old GPU in PCIe slot works first time.  The system just doesn't like the GT740 GPU!
 
Suggestions?  I'm fast approaching the point of just returning it...

Thanks.  I should have added that I spent hours trying to dig out updated BIOS from HP's website and failed...only as-shipped drivers and BIOS is available there.  Useless...no wonder HP quit/sold off their PC division.  Any use in trying to get BIOS directly from AMI, or asking for trouble?
 
Strange that a 11 year old Dell will run the 740 but not a 4 year old HP.

bob16314
Your HP PC/Mobo probably doesn't support graphics cards newer than the NVIDIA 600 series cards, this is not uncommon..Contact HP support or go to the HP support website for your PC and see if there's a BIOS update to improve graphics card compatibility that might fix it..If there is not, well, you can most likely fugeddaboutit, sorry to say.

+1
 
Have had issues with HP product in the past.  Long time ago; call HP support  ---> answer only 3 specific GPUs would work in their MB.
 
You will need a GPU that can bypass the on-board GPU on its own