Power management flakiness

Hi -- I have a new laptop running XP2 SP3. The power management options are
not obeying my commands. I set the "plugged in" option to blink off after 1
minute, and most of the time nothing happens. Occasionally, while I fiddle
with it, the screeen will go dark as oredered, but even then it pops back on
after 1 minute and stays on. Totally maddening. Anyone have any ideas? Thanks
for your help. -- David