how to set up boot drivers plz help

[aaroncam]

just built a new computer with every thing being new other the the one hard drive that has the os on it but i cant dont know to make it boot from it , plz help

 

[SkyNetRising]

Reinstall OS.
Since you replaced motherboard, re-installation of OS is highly recommended.

 

[kanewolf]

MERGED QUESTION
Question from aaroncam : "how to set up boot drivers plz help"

just built a new computer with every thing being new other the the one hard drive that has the os on it but i cant dont know to make it boot from it , plz help