Just to add to this for future User's experiencing similar-related boot-up
Normally when User's get: "Boot-manager cannot be found" during reboot/start-up -is due to the incorrect: Disk Priority Device being set within you're Bios Settings.This Error-Message can occur when unplugging/changing Sata-Ports on your Mobo as well. On Win7(depends on one's Bios Manufacturer mostly)press Delete-Key(yours may differ)repeatedly right when rebooting.
Then choose Advanced Bios Features/or Similar Tab. Once there click Advanced Disk Priority BootSequence.Now, click Enter on the first one & choose enable on whichever is your Main Disk/OS to boot from. Click F10 key on keyboard to Save and Exit to reboot.
*Just a note:
If you have no disk for your OS and have an OEM OS installed into your Computer,one can click the F8 Key(yours may differ)to Repair Computer, or select: Last Know Good Configuration that Worked & etc., Options.