ca75 on "Solution for Permission Errors on Restore Jobs"

I thought I'd share this tip. I'm a self-taught admin in a very small business, and perhaps this is obvious to more experience and trained. It was not obvious to me.
I was in a disaster recovery situation this week with a Windows SBS 2003 Server (yes, I know this is very out of date) running as a virtual machine in XenServer 6.5. After reverting to a clean machine snapshot, I attempted to use iDrive to bring System State and files back to current. I spent more than two frustrating days trying to restore-in-place, and hit the same combination of permission errors, insufficient space, and 0KB restore files. The iDrive software was essentially useless at that point, and I was unable to get a solution from tech support.
What I needed to do, and finally did, was a create a Windows user in the Backup Operators group. Apparently builtin administrator was insufficient. I ran iDrive as this new Backup Operator, and restore-in-place smoothly.
I hope this might help someone else.