On starting up PC last line reads CMOS checksum error - defaults loaded

When I switch my pc on, it does not load up as normal, but black screen shows GA-8S648 F1
Check System Health OK, Main Processors: Intel Pentium (R) 4 2.80GHz (133x21) <CPUID:0F29 Patch ID:0011> Memory Testing: 1048576K OK
Memory Frequency : DDR266
Primary Master : WDC WD1600AVJB-63WTA0 58.01H58
Primary Slave : None
Secondary Master : Pioneer DVD-RW DVR-107D 1.10
Secondary Slave : ASUS DVD-E616PZ 1.03
CMOS checksum error - Defaults loaded
 
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