have switched batteries to no avail. every time i boot, it gives two beeps and says "check date and time settings". when i go into bios, the clock has started at 00:00 with seconds ticking. the date says 01/01/1990. i set it right, f10 then reboot and it does the same thing. are there jumpers on some mbds that reset the date/time at boot? or is this a bad bios chip?