Win7 system bootmgr is missing do not boot?

Your problem is because the C disk is set to active partition under Win7, the C disk is set to the active partition after the original Win7 100MB of space becomes inactive partition, resulting in system startup, unable to find the corresponding boot file under C disk.

Because the system has failed to start, after this failure, you need to use WinPE to boot,

After entering the PE, in Disk Management, the right key system retains the partition, select: Mark the partition as active partition, then reboot can enter the system.