Power Meter Plus provides constant laptop battery updates
Or you can install Power Meter Plus. This free utility for Windows XP and earlier releases provides a detailed battery meter which is always present on your desktop. The meter is partially transparent, so you can see through it. And it lives on the right or left side of the screen. If you need to access something hiding under the power meter, just move your mouse over it and the meter will jump to the other side of the screen.
As your battery power drains, the meter will get brighter. And you can configure Power Meter Plus to show notifications when the battery reaches critical levels.