XPS 8900 won't boot with external hard drive connected

It had System Config -> USB Config -> Enable Boot Support unchecked and still wouldn't boot to the correct hard drive. 

That said, it seems as if I may have found the solution:

The reason why it wouldn't load was because of something to do with windows boot manager not recognizing my primary hard drive and/or placing it in lower precedence whenever an external hdd was detected. Since there isn't a clear way to change boot precedence in windows boot manager, I had to get around that. In order to do that I had to create a new boot option and set it to run before windows boot manager. I tried this before, but I don't think i had the right file selected to boot to.

I did the following and my computer now seems to be booting like it's supposed to. 

1. On startup tap F2 a bunch of times before or at the very beginning of the dell logo screen in order to enter the BIOS.
2. In BIOS, go to: General -> Boot Sequence 
3. Make sure UEFI is selected.
4. Click the "Add boot option" button
5. A prompt for creating a new boot option will come up with three fields. 
6. On the name field you can type whatever you like (i used bootx64.efi, you'll see why shortly)
7. On the file system field, make sure that the paths referencing your boot drives are selected. -- If you have the USB boot option mentioned in the above comment enabled, you may see other fields here referencing the USB drives. Make sure they aren't highlighted.
8. On the file name field, click the button with three dots and navigate to \EFI\Boot\ and select bootx64.efi
9. Save your new settings
10. You should see a new checkbox up top with the name of the boot option, make sure it is checked.
11. Click on the white box for the new boot option on the right and use the arrows to move it above "Windows Boot Manager"
12. Click the Apply button on the bottom of the screen. 
13. Click Exit
14. It should now boot to your C drive with windows like it's supposed to.