RAM not recognized

I'm trying to help a friend with her Compaque Presario 2266 computer. The ram is upgraded to 256 with two RAM chips that have been checked and double checked to make sure they are the correct ones. The computer runs fine except it only recognizes the amount of RAM that I took out. Strange! I've rebooted, reopened and checked everything twice. Went to the Compaque (HP) site and spent hours with no results. Can anyone help?
Compaque Presario 266
Pent II 30 MHZ
Windows 98
64 mb to two 128 mb

 

I presume you have tested the RAM modules one-at-a-time in the system in all slots to see if there's a problem with a slot, right? Do that with both modules.

 

Thank you -- I will try that tomorrow when I'm at her house. I did find a "help" file that said to disable the CSMO then reboot. Does that sound feasible? I'm in an area that I know very little about when it comes to messing with the BIOS and CSMO.