Please provide model number of the main board, if you can. Or the model number of the computer.
Also, what is the exact error message?
One of these?
BIOS ROM checksum error
System CMOS checksum bad - default configuration used
Press <F1> to resume, <F2> to Setup
CMOS Checksum Bad
Press F2 to Run SETUP
Press F1 to load default values and continue
CMOS Checksum Error - Default loaded
Often thee is some option to confirm and enter BIOS.