I can't Enter Cmos!

what do u think culd be the cause of my pc not entering CMOS setup? this is because i need format my harddrive but i can't go into cmos.
what i did was to take the hard drive to another pc, formatted it there, when i brought it back to that same pc, it refused accepting the hard drive!

N/B: this  system has refused 2 hard drives that worked in other systems

please this is has given me sleepless night. culd it be that the board is bad?
please comment