Can't boot with external hard drive connected

[Yokeko]

Apparently, my Bios is not setup to start my system from the operating system (Windows 10) on my system hard drive. Rather the BIOS is setup to try to boot from a CD-ROM first, from a USB drive second and from the hard drive on my system third. As a result, when I try to boot my system with the external hard drive connected, I get the following message:

An operating system wasn't found. Try disconnecting any drive that doesn't contain an operating system. Press any key to restart. That works, and I'm then able to boot the system. When the external hard drive is disconnected, the system boots as it should. 

What this tells me is the BIOS needs to be modified to include my system hard drive in first position. But I've been unable to figure out how to do that. Best I've been able to do is to go to the HP Setup Utility and restore Factory Settings -- but that doesn't seem to solve the problem. By the way, the BIOS on my system is the latest version available.

Your advice will be sincerely appreciated.

[WAWood]

@Yokeko 

I'm presuming that by "modify the BIOS" you actually mean "change the settings".

Legacy BIOS generally only allow for three boot devices, so any attached fourth device will not be seen.

Also, they often DO NOT allow booting from external drives -- but to try this, disconnect the CD/DVD device before you reboot.  Then, you need to have the drive connected when you're changing the BIOS settings and seeing if it shows up in the list of boot device options as the third device (now that the CD/DVD device is gone).  IF it does not, you're not going to be able to boot from it.

[Yokeko]

Thanks for your response. And, yes, I meant "change the [BIOS] settings".

All I want to do is to change the BIOS settings so I can boot my system with my external USB hard drive connected. Here's what I'm seeing on the Boot Order screen:

UEFI Boot Sources

     USB Floppy/CD

     USB Hard Drive

     ATAPI CD/DVD Drive

Legacy Boot Sources

     Hard Drive

          SATAO

          USB Hard Drive

     ATAPI CD/DVD Drive

     USB Floppy/CD

     Network Controller (xxx)

Given the above current boot order, what's your advice on how the make the necessary changes so my system will boot normally with the external USB hard drive connected?  

[WAWood]

@Yokeko 

Thanks for the info -- but based on your posting, you have a newer PC that has both BIOS and UEFI settings.

What you posted is the Boot Devices menu -- and all that does is LIST the devices so you can choose one.  IF the device you want is not shown there, then you obviously can not select it.

You would have to go elsewhere in the settings to change the default ORDER of the devices, and sorry, In do not know specifically where that is.

[Yokeko]

Your comments were appreciated.

Although HP has made the process of modifying the order of devices difficult to comprehend, I was able to make the hard drive on my system the default drive. Turns out you can change the device order within the Boot Devices menu. I can now boot my system with my USB external hard drive connected. 

Thanks for taking the time to help.

[WAWood]

@Yokeko 

Glad to hear that you got it working.