I won’t go into great detail here but in short, if VSSAdmin is not letting you delete shadow copies and is throwing this message:
There is another (less safe…) program called DiskShadow which will.
It’s built into windows server… and using it to get rid of pesky shadow copies that won’t otherwise goes away looks like this:
DISKSHADOW> Delete Shadows All
and away they go…
One of the best blog articles I came across that details both VSSADMIN and DiskShadow tool and why VSSAdmin sometimes falls short is here: