Hi,
Thank you for posting in Microsoft Q&A forum.
Have you set the task sequence variable before using it? It appears that you have to pre-set a custom variable then reference that variable name in this task sequence step.
For more information, please refer to:
Variables for Format and Partition Disk
Managing Multiple Hard Disks in a Task Sequence with MECM
Setting the drive letter during an Operating System Task Sequence
Please note: The links are not from Microsoft, just for your reference. Thanks for your time.
Best regards,
Simon
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