Welcome to these forums.
The computer has a battery that is either on the motherboard or attached to the motherboard. The battery's purpose is to preserve the CMOS configuration information (CMOS setup) when the computer is powered off.
CMOS BATTERY
The error messages indicates that either that battery is missing or it is past it's useful life (probably the latter).
Once the battery has been replaced, the "TESTING CMOS BATTERY ... FAIL" should change to "TESTING CMOS BATTERY ... PASS"
Examples of common batteries that attach to the motherboard via cable are:
1.
http://members.dodo.com.au/~slappanel555/misc/BATT_1.JPG
2.
http://members.dodo.com.au/~slappanel555/misc/BATT_2.JPG
If you can't find the battery, look on the motherboard for a device that looks like what is pictured at
http://members.dodo.com.au/~slappanel555/misc/ds1287.jpg
If it turns out that you have one of those (or similar), let us know because there can be complications in it's replacement.
CMOS CONFIGURATION
After replacing the battery with new, the "TESTING CMOS CHECKSUM ... FAIL" will still be present. To fix that, you will need to run a setup program to reenter the lost configuration information. The computer appears to be dated about 1991, and so the computer may have a built-in setup program. Look for something like "Press DELETE to enter Setup" when the computer is powered on.
Being a 286 based computer, a generic setup program should work. Let us know if you need one (i.e. no built-in setup).
And let us know if you need help in determining what configuration to enter.
