Whenever my computer reaches around 5% of its battery level, it shuts down without saving my work. Under advanced power settings, I have the Critical battery action set to to go sleep when the the battery reaches the Critical battery level, which is set to 8%. Is Windows starting to put my computer to sleep but halfway through, it runs out of power and then suddenly shuts down? Is 8% of my battery not enough power to put the computer to sleep? Or is there actually less than 8% less and my computer simply is not calibrated?

I also have the Low battery action set to notify me when the battery reaches 15%, but all I get is a subtle bubble on the bottom right that I usually do not even notice. Can I program Windows Vista Home Premium to also beep, like I used to be able to do on older versions of Windows?