Normally, a Windows installation on a laptop computer displays the laptop's remaining battery power as an icon in the system tray. Sometimes, however, this icon may disappear. If reactivating it normally doesn't work (by right-clicking the taskbar, clicking "Properties," "Notification Area" and checking the "Power" box), you can try this trick with the Windows Registry Editor to reset your taskbar icon settings.
Click "Start," "Run." Type
and press "Enter." This will bring up the Windows Registry Editor. The left pane displays registry keys in a hierarchy similar to a computer directory tree. Clicking on a key will bring up one or more editable values in the right pane.
Navigate to the "HKEY_CURRENT_USER\Software\Classes\Local Settings\Software\Microsoft\Windows\CurrentVersion\TrayNotify" key.
Right-click on the key, click "Export" and save it anywhere on your computer. Remember where you've saved it---that way, if the registry modification you're about to make causes problems, you can simply double-click on the saved registry file to restore the original settings.
Click on the key to select it. Some values should appear in the right pane. Delete the "IconStreams" and "PastIconsStream" values by right-clicking on each one and selecting "Delete." Close the Registry Editor.
Open the Task Manager by pressing "Ctrl," "Shift" and "Esc" or "Ctrl," "Alt" and "Del." Click the "Processes" tab, and find the process called "explorer.exe." You're going to shut this process down, so that when it restarts it will use your new registry settings. Click on the process, then click "End Process."
Click the "Applications" tab, then click "New Task." A window similar to the Run window will appear. Type:
and press "Enter." This will restart the Windows shell.
Check the system tray for your missing icon. If it isn't there, it probably just needs to be re-enabled using the method described in the introduction.