XPS 8900, manufacturing mode

In a motherboard replacement, the original service tag must be entered into the BIOS. If it is not entered, the system will only work in Manufacturing Mode. Even if the BIOS is changed, the motherboard will continue to work in manufacturing mode until the service tag is entered. Also, by not entering a service tag, the boot sequence will revert to the network as the first option. Network boot can only be disabled by entering the service tag of the system.

Service Tag field
* Find the service tag number on the label on the rear of the tower
* Power on
* Press F2 to enter the BIOS
* In General- System Information, look for Service Tag. It is blank. Enter the service tag number from the label
* Exit the BIOS saving the change

SERVICE_MODE two pins
Look on the motherboard for SERVICE_MODE two pins. If a plastic jumper is on those two pins, remove the jumper and place it on PSWD two pins

Did you change the boot order in the BIOS?
"the boot sequence will revert to the network as the first option"

ok so I did all of that, still no go.After the Dell logo, I get two on scr2een messages1

Post pictures of the BIOS main screen showing the tag (I will delete it). Then post a picture of the Boot Sequence, Advanced Boot Options, and Secure Boot.

I thought these were our defaults?
* General- Boot Sequence = Windows Boot Manager, UEFI
* General- Secure Boot = Enabled

the only option i remember changing was the boot sequence and the sata mode

i did

Check those I listed. If still no go, hopefully another Desktop user will reply. If not, you will need to contact Technical Support and see if they can figure this one out.

ok so 

* General- Boot Sequence = Windows Boot Manager, UEFI
* General- Secure Boot = Enabled

I did the first option but I was unable to choose the 2nd option because it said that Secure Boot was not available when not using Legacy boot.

But thank you so much! My system booted. Gonna add all the my peripherals and what not. Any precautions or steps I should take to avoid this from happening again, or rather will my system be normal again?

Since it is working now, for future reference, I would take pictures of the BIOS pages current working settings and save them to a USB key. Then, you can refer to them later if something happens.