Make sure the CMOS clearing pins are not set to clear the CMOS. Review the setting to see where they should be. Next, some newer mtrbd. bios won't allow too an extreme setting not capable or not reflecting what's there or something is in error and won't proceed. Make darn sure the new battery is at true contact with the battery.
It always helps to give details, you didn't give much.
I tried reseting the cmos, and changing the cmos battery with a new one, but the settings never save. Next time i boot up the computer they are gone. How can i fix this?