The MSR partition is required to boot Windows 7 and later operating systems. Ordinarily, this partition does not have a drive letter assigned to it. If a drive letter is assigned then this can cause problems with Microsoft Volume Shadow copy Service (VSS).
If you receive the following error (or similar) when the MSR partition is included in a disk image then removing the drive letter association should resolve the issue:
Backup aborted! - Failed To Create Volume Snapshot Result Code: 0x8004231f
1. Start the Windows Disk Management Console. Click 'Start', type 'diskmgmt.msc' (without quotes) and press ENTER.
2. In the Windows that opens, right-click on the 'System Reserved' partition in the lower pane and select 'Change Drive Letter and Paths..'
3. In the dialog that opens, click the 'Remove' button.
4. Close the Disk Management Console and restart Macrium Reflect.
After removing the drive letter create a fresh image of your system including the MSR partition.