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