Checksum Error

Probably a dumb question, but whenever i turn on my computer i get a checksum error, it asks to hit F1 to continue, or to enter the BIOS, if i continue to boot sometimes the processor shows up as 277, sometimes 233, somtimes 266, it's and old pc as u can tell....also whenever i change the date in the BIOS and then power off the computer it doesnt save the correct date...any help or direction would be much appreciated, thanks in advance....