P7-1287c won't boot with PCIe 3.0 video card. Any suggestions?

[Rwolf01]

I have a Pavilion P7-1287c, running Win10-64.   I installed a ZOTAC GeForce® GTX 1060 3GB graphics card, with the secondary 6-pin power connector.  On power up, it will detect the video card and send video out the card's HDMI port, but then it hangs before showing the Startup Menu.  (PC will beep once about every 5 or 10 seconds) 

If I boot the PC w/o the card, msinfo says the BIOS is 7.16 booting in Legacy mode.  

This post suggests that I need to be booting in UEFI mode for the new card to work. 
https://h30434.www3.hp.com/t5/Desktop-Boot-and-Lockup/Pavilion-p7-1500t-UEFI-or-BIOS/td-p/6133801

Is that correct?  Is there an easy way to convert my current boot disk, or do I need to reinstall the OS?  

[banhien]

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@Rwolf01 wrote:

.. If I boot the PC w/o the card, msinfo says the BIOS is 7.16 booting in Legacy mode.  

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@Rwolf01 

Your machine with BIOS 7.16 won't work with GTX 10xx full stop.There is NO newer BIOS for your machine

                https://support.hp.com/us-en/drivers/selfservice/HP-Pavilion-p7-Desktop-PC-series/5187022/model/5192...

Regards.

[Rwolf01]

Can you elaborate on why it won't work?  

In this post an HP employee explicitly recommends the ZOTAC GeForce GTX 750Ti 2GB GDDR5 PCI Express 3.0

https://h30434.www3.hp.com/t5/Gaming-Accessories/Graphics-card-for-P7-1287C-Pavillion-motherboard-Bo...

Why would one Zotac PCIe 3.0 GTX card work, and the other not?

[Rwolf01]

Update: There is a (sort of) easy way to convert a Win10 boot disk from MBR/Legacy to GPT/UEFI...

1:  delete the HP recovery partition to get dow to 3 partitions total.  
2: click settings->Update&security->Recovery->Advanced Startup->Restart Now.
3: In the reboot environment select Troubleshoot->adcanced options -> command prompt
4: log in to an administrator account.
5: slaughter a goat, place warm entrails on the hard disk and type MBR2GPT.EXE /CONVERT

6: type Exit then select turn PC off.
7: Reboot and select the hard disk or Windows Boot Manager under UEFI Boot in the Boot Options menu. 
8: Log in as normal, type MSINFO to confirm that bios mode is now UEFI. 

That all actually worked, but when I install the GeForce GTX 1060 card and reboot it behaves the same.  Text video output comes out the HDMI port of the GTX card but once it gets to where the BIOS Startup Menu should appear it hangs. The motherboard beeps once, for about 1/2 second, every 25 seconds.   

Removing the GTX card allows it to boot normally again.