Hope someone can help.I got a second hand motherboard off ebay when it boots it shows CMOS checksum error and I have to press F1 to continue. I believe this error is caused by the loss of the bios settings and the default settings are loaded. I know the common cause is a low battery but have tried several and cleaned the battery terminals all the same. If I change anything in the setup it will reboot again ok within a short while but anything longer than 5 minutes and the error is back again. Has the board itself had it?