Installed additional RAM, but the computer... due to non-pairing of RAM.

Cause:

The computer may not recognize additional RAM for the following reasons:
The RAM has not been added in pairs.
EDO RAM has been mixed with non-EDO RAM.
The new RAM chip is bad.

Solution:

Consult the owner's manual to find out what the proper configuration of RAM should be. Reinstall the RAM in the proper configuration. If correct, contact next level support to resolve the RAM issue.