Th computer in question has a small SSD as c: where Windows 10 is installed. However, the 100MB System Reserved partition d: is (for whichever reason) on a large, old HD which is developing problems.
I tried to remove this HD, but then the system is no longer bootable at all.
Is there a way to make the system bootable from c: without having to reformat it?
Disk Management shows c: as Healthy (Boot, Page File, Crash Dump, Primary Partition)
d: appears as Healthy (System, Active, Primary Partition)