how to reenable bios for toshiba l645d

[dekibe]

i wanted to instal window 8 on my laptop then when i pressed f2 it displayed that boot manager is missing .since then when i switch on it start up directly...pliz help
thanks inadance

 

[das_stig]

Turn on and hold the number 0. Select factory default and follow the directions.

This will only work if you have deleted the recovery partition when installing Windows 8. If you did, I bet you didn't make a set of recovery DVD's that you get prompted to do by Toshiba software?