I found this issue with the Libretto 100 that Michal Dudek kindly sent to me. If the BIOS on the system is an old version (the version on this Libretto was in the V6 range), ACPI is NOT supported on Windows 2000/XP. This means that we potentially don't get as much time out of the battery, as ACPI provides energy saving features that APM may not. The trick to solve this, is simply update the BIOS. I've now updated it to the latest V8.10, and I now have full ACPI support on Windows 2000 (after re-installing it, Windows 2000 wouldn't let me change the Hardware Abstraction Layer from Standard PC to ACPI compliant system without totally failing).

I have here the latest BIOS version for those still using an older BIOS version (Libretto 100/110/100CT/110CT only!). http://download.josephn.net/?file=libretto_110_100_bios_latest_v810

In the self extracting ZIP, are two files: BIOFCE5T.COM and CHGBIOSM.EXE. Make a DOS bootdisk, ideally one with as little stuff on it as possible http://www.bootdisk.com/. Get the ones designed for driver free BIOS flashing off Bootdisk.com. Make the boot floppy, then drag both files BIOFCE5T.COM and CHGBIOSM.EXE onto the floppy. Please make sure you are using a good floppy, as this could cause many problems later

Turn off the Libretto, connect the floppy disk drive, and insert the bootdisk with the BIOS files. MAKE SURE THE AC POWER IS CONNECTED. Turn on the Libretto, it should boot off the floppy. Run CHGBIOSM.EXE, and when asked for the BIOS file, enter BIOFCE5T.COM

Hit Enter. DO NOT TURN OFF THE LIBRETTO UNTIL THE TOOL TELLS YOU THAT YOU CAN RESTART OR TURN OFF THE POWER

If the flashing was sucessful, then you can proceed to install Windows 2000/XP, which should detect that you have an ACPI machine in setup!