You may view your hard drive in Disk Management and see unallocated space. The space will be on the hard drive, but Windows cannot use it. It is like having a spare room in your house but locked off.

Is there software that can extend the C drive partition on one disk to unallocated space on a different disk? I know if you have two partions on the same disk it can be done (C and D on Disk 0) but ...

The System Reserved Partition or EFI System Partition on your hard drive is a tiny sector Windows uses to house system files such as the Boot Configuration Database, Boot Manager Code, and Windows ...