When installing Windows, the install will create the system reserved partition and a larger partition for the operating system. When this happens the trick is to delete the larger partition and then stretch the system reserved partition. Do this so the system reserved partition is large enough to hold the operating system.
Second option would be to mark the operating system partition as active and then use the install media to repair boot files. Afterward you should be able to delete the system reserved partition* because it is no longer needed.
* I'm assuming the repair will not switch the active partition back to the system reserved partition. If that happens you will need to boot to a partitioning software boot disk and delete the system reserved partition, before repairing boot files.