You aren't likely to get any help on the forum regarding passwords. It is simply not allowed per forum rules.
Are you saying that you placed a password on the BIOS and that you can't remember it?
When you start the system can you press a key to select the boot device (without a password)?
If you can select your boot device, simply re-install from the recovery disks to get a complete install in place (sorry for stating the obvious).
The boot manager missing error is a result of an incomplete installation of the recovery disks. Good luck!