Windows Power Management

Power management in Windows (XP) seems so iffy and unpredictable. Often, I will find a drained battery when I power up my laptop 4 hours after shutting it down at the end of the work day. What seems to happen is that after I invoke Shut Down on my laptop--which takes a bit of time, especially if connected to the corporate network--and I flip the screen closed, that action--flipping the screen--invokes Sleep mode. Instantly, thus over-riding the shutdown in progress.