CMOS Settings Changed by WinXP

Hi,

I have an old IBM Thinkpad T23 laptop computer. Recently, I have
trouble with the display, black, when I first power up the laptop. After
WinXP boots up, I hold down the Fn key and press F7 (int/ext display)
key to get the display turned on. I often have to do this more than once.

Note: I recently replaced the CMOS battery. I changed the BIOS
(press F1 at power up) setting for "boot display" from "both" to "LCD".

I SAVED the change, but the next time I boot up the T23, I have
the same issue. I reboot the T23 and press F1. BIOS settings, the
boot display is back to "both".

Does anyone know why WinXP changes the BIOS setting?

Thank You in advance, John