I deleted all shadow copies, first via Disk Cleanup and then via vssadmin, all per your instructions
. It didn't help. I then went in and disabled System protection. It didn't help either.
Disk manager still says I only have 462756 MB shrink space out of a total of 953867 MB (NTFS), leaving 491111 MB after shrinkage. That's not enough - I need to shrink the C volume to 96 GB, because I want to move to my empty RAID SSD (2 disks/mirror) with 107.13 GB (NTFS).
Can it be done?
(I assume the reason I cannot use Seagate's disk utility to execute the move is that it cannot move from a larger partition to a smaller, but it hasn't actually told me that - it just doesn't follow instructions.)