Opti-plex Gx110 No Boot Sequence

I have an Opti-plex GX110 that I got from a school computer sale. It has a Pentium III 800MHz processor with an A08 BIOS. There was no CMOS battery on the motherboarc when I got it. I installed a battery from another Opti-plex GX110(was working). I booted up the computer and pressed F2 to access setup. When I checked the boot sequence the only component listed was the 3.5 diskette. I have tried to install Windows 2000 from the OS CD,since no CD-ROM or hard drive is listed in the boot sequence the computer access the 3.5 diskette, but when it cannot find what its need to continue the installation it tells me to press F1 or F2. If I press F1 it tells to press F1or F2. If F2 is pressed I access setup.

Is it possible to reestablish the boot sequence listing in setup??? If so how?? or is the mother bad.

 

can someone help ????

NOTE: Replaced the battery in the other Opti-plex tried to boot ..it now has the same problem as the one with the 800MHz processor..