cmos checksum error

[vard]

sorry if this is in the wrong place or you have had this question before.

hi i have just go a new mb cpu and pci graffics
mb-nforce4 939 k8 ht2000
cpu- amd64 3200
pci graffics-asus extreme n6200tc
60gb hd been reformated and 512 ddr400 ram
put it all in new case started up but ran an error cmos checksum error
looked every were on the net for help all say samething so i have tried most things . new battery check the housing unpluged it all and tried out side box pluging each device one at a time no look, can go into bios but each time i save i have to jumper the cmos to get first boot screen and there is no os in it as when i press f1 it carnt find cdrom so i start it up again after restting cmos un pluged hd and left cdrom when i pressed f1 it aloud me to run from cd and it work started installing xp pluged in hd got past partition but when it rebooted it locked up and i had to reset cmos againa so ilike have said read most thing on this even a guy that got a replacment mb and it still happened please please help im pulling my hair out here im at a :dead end so any help well be most welcome as long as its not to do with the battery lol tried it all sorry.and i know that if you clear cmos you will get the same error