Two system drives (when making a backup)?

When making a backup Win 10 insists that my D: 'games only' drive is a system drive too? and wants to back it up.
I never have had any Op-sys installed on it, what are the easiest way to find out if it have any system related stuff added on it, and if it have none, then how to remove the 'system tag' from it?

  

(never mind the F: set as active, it's not now)

And checked with diskpart that there actually only is one system drive.

 

Also get this when changing HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionWindowsBackup validconfig 0 and validsystembackup 0

 

I actually bump this one, as I still have the same problem, that 'System image' want to backup my D:too, that is my Steam and other games only drive! And nothing tells me it has system files (more then any other drive) except event viewers backup. (Long text coming up) /IsCritical="1" BackupTypeDetermined="1"
I really really want to be able to backup only system!

BackupTarget

F:

NumOfVolumes

3

VolumesInfo

<VolumeInfo><VolumeInfoItem Name="D:" OriginalAccessPath="D:" State="14" HResult="0" DetailedHResult="0" PreviousState="9" IsCritical="1" IsIncremental="0" BlockLevel="1" HasFiles="0" HasSystemState="0" IsCompacted="0" IsPruned="0" IsRecreateVhd="0" FullBackupReason="0" DataTransferred="264780251136" NumUnreadableBytes="0" TotalSize="264780251136" TotalNoOfFiles="0" Flags="520" BackupTypeDetermined="1" SSBTotalNoOfFiles="0" SSBTotalSizeOnDisk="0" /><VolumeInfoItem Name="C:" OriginalAccessPath="C:" State="14" HResult="0" DetailedHResult="0" PreviousState="9" IsCritical="1" IsIncremental="0" BlockLevel="1" HasFiles="0" HasSystemState="0" IsCompacted="0" IsPruned="0" IsRecreateVhd="0" FullBackupReason="0" DataTransferred="43444207616" NumUnreadableBytes="0" TotalSize="43444207616" TotalNoOfFiles="0" Flags="1546" BackupTypeDetermined="1" SSBTotalNoOfFiles="0" SSBTotalSizeOnDisk="0" /><VolumeInfoItem Name="" OriginalAccessPath="" State="14" HResult="0" DetailedHResult="0" PreviousState="9" IsCritical="1" IsIncremental="0" BlockLevel="1" HasFiles="0" HasSystemState="0" IsCompacted="0" IsPruned="0" IsRecreateVhd="0" FullBackupReason="0" DataTransferred="336986112" NumUnreadableBytes="0" TotalSize="336986112" TotalNoOfFiles="0" Flags="520" BackupTypeDetermined="1" SSBTotalNoOfFiles="0" SSBTotalSizeOnDisk="0" /></VolumeInfo>