The default configuration of Mandriva on an eee works very well, but there are some tweaks that will help to maximise the battery life.
The default KDE installation will start Kerry Beagle. Beagle is a background daemon which will constantly index your disc drives, and Kerry is the KDE front end for Beagle. The Beagle daemon runs when the CPU is idle which will prevent the CPU entering its lowest power state and waste energy. If there is an icon of a dog in the system tray left click on it and select 'Configure'. Disable the daemon and stop Kerry from automatically running on log in.