HAVING PROBLEM WITH CMOS CHECKSUM ERROR..

i am having problem with my pc. last friday, when i boot up my pc..i hear a long beep.. i first thought that my cpu overheat.. i clear cmos data… i also remove the memory and put it back..when i boot up my pc..a message was displayed :

checksum error-default loaded
cpu has been change or cpu ratio fail.
change cpu setup,save before exit.

i change the time and date..i save before i exit..my pc restart…all are normal, but when i shutdown my pc and boot it..the error message always appear..what will i do???