CMOS checksum error
Bad or old CMOS battery
Reboot the computer. If error still occurs after rebooting the computer enter CMOS setup and check all values, this includes verifying the time and date are correct. Once everything is verified and changed, make sure you save settings and then exit CMOS setup.
If everything appears to be correct, you can try resetting the CMOS to the default values. After the CMOS values are reset, save changes and exit the BIOS to reboot the system.
If this issue continues to occur after you turn off your computer, the CMOS battery may be failing or already bad. Before considering replacing the CMOS battery, try leaving your computer on for several days. Sometimes leaving the computer can re-charge the battery.
Computer improperly turned off
If the computer lost power while it was still running, it may have corrupted the CMOS. Make sure the computer is ready to be shut off before turning off the computer. If you have a laptop computer, make sure the battery is charged before disconnecting the power connection.
If the CMOS values are corrupt, enter the correct values in CMOS setup and then save and exit CMOS setup to resolve your issues.
BIOS update recently performed
If a BIOS update was run on the computer, the values stored in CMOS may have been reset. Enter CMOS setup re-enter all values and then save and exit CMOS setup.
If you cannot enter the CMOS setup, or the computer no longer keeps its BIOS values, the BIOS update may be corrupt. In this case, we recommend updating the BIOS again or reverting to an earlier version.