The only way I know of restoring the CMOS settings is to do it manually. During boot-up, assuming that you've cleared the problem that caused the lack of display, you will get a message saying which keyboard key to press to enter setup. Once you are in the CMOS setup screens you need to make any necessary changes. These days BIOS default settings are generally mostly correct and few changes - if any - are needed. You need to read the motherboard manual carefully to know the effect of any changes.