Hello David,
Thank you for posting your query on Microsoft Community.
I would appreciate if you can provide us the following information to help us understand the issue better:
- Is it external hard drive, which is attached to this DVR?
- What is the make and model of your external hard drive?
If you are trying to format a hard drive attached to your computer or an external hard drive. You may refer to the Microsoft help article and check if that helps.
Refer:
Create and format a hard disk partition
Note:
Formatting a volume will destroy any data on the partition. Be sure to back up any data you want to save before you begin.
Hope the information provided is helpful. Do let us know if you have any queries related to Windows, we will be happy to assist you.