XPS 8900, trying to boot from USB device

Use F12 from the Boot Dell Logo screen to access the proper menu. The USB drive must be connected when you do this, and it will appear as a boot choice. This is not in the BIOS that can be set.

Now if I read this wrong, and you have it booting from the USB drive all the time and not the HD, then the HD could be bad or damaged?

More details would help here. Especially if this is a NEW instance or had always done this and you want to change it?

replace cmos battery with a new one then clear cmos settings via mobo jumper.

try a clean install of OS on your boot drive installed inside 8900 (hdd or ssd).  wipe the external usb drive clean before reconnect to pc.

@ispalten​ 

Thanks so much. 

I replaced my hard drive as it had become full with a SSD drive. I had to reinstall windows 10 and the machine now boots beautifully with the new C drive. However, if i plug the external SSD drive, it wont boot.

I will try your plan of going into the bios with the drive plugged in to see if I can change the choice.

This is what i see on the BIOS with teh drive plugged in. I cant see any option to choose a boot option.

Thanks again anyone wh can help!

Docwold

windows boot manager contains the boot link to your boot device.  the device itself does not show as a discrete device on F12.

the only time a UEFI boot device would show on F12 is if you plug in a bootable USB that has UEFI boot file (such as MS installation media USB) or a bootable DVD loaded in an external dvd drive (such as MS installation media burnt on a DVD), or a SSD/HDD that has OS installed in UEFI on another PC and is then transplanted to the current PC.

If a SSD/HDD has its OS installed natively on the current PC, the device itself would not show on F12, but Windows boot manager.

@Docwold​

@ispalten​ 

I will try your plan of going into the bios with the drive plugged in to see if I can change the choice.

Did you read what I said, "Use F12 from the Boot Dell Logo screen to access the proper menu. The USB drive must be connected when you do this, and it will appear as a boot choice. This is not in the BIOS that can be set."?

Again, you can not set the BIOS to boot the PC from a USB drive. You must PRESS Function key F12 when the Dell Logo is up. On THAT menu you WILL see a USB drive, providing it has a bootable item on it that it can see, AND the drive must be connected before you power the PC up or do a REBOOT.

Some wording is confusing.  "However, if i plug the external SSD drive, it wont boot."  Are you always trying to boot the OS externally, or is this a different SSD used for storage?

You also said "I  had to reinstall windows 10 and the machine now boots beautifully with the new C drive."  If it's not booting with an external storage drive connected, try booting with it disconnected.  Connect once booted to use for storage.