Sometimes, when used SCCM + MDT combination, I have noticed this task sequence error with code 0X800700A1. The reason for this is that the HDD/SSD drive in the machine is incompatibly formatted – the task sequence could not find a partition on the drive to write on. Even when we use some kind of diskpart formatting during the task sequence, especially some new Dell laptops sometimes require a special treatment.

A solution for this one is quite easy. You will need to have a debug (F8) console turned on in your boot image. After booting it up and receiving this error, open the debug (console) window and type in following commands, one by one:

list disk
select disk 0
(convert gpt) - this one is probably not needed, but it helped me at some point too
create partition primary
select partition 1
format fs=ntfs quick

After that, reboot the machine and start up the OSD once again – it should no longer fail with the mentioned error code, as the system drive is not correctly partitioned.