How to Update Power Management Drivers on a Laptop
Most often, power management issues are resolved by obtaining the latest version of your laptop’s ACPI power management software, or device driver. Ensuring that you have the latest version is something you should do; the Windows Update program may not look for new power management software for you.
The easy way to check for new power management software is to follow these steps:
The System window appears.
Open the Device Manager.
In Windows 7 and Vista, click the link on the left side of the window: Device Manager. In Windows Vista, also click Continue or type the administrator’s password.
In Windows XP, click the Hardware tab. Then click the Device Manager button.
Click the plus sign (+) next to System Devices.
Right-click Microsoft ACPI-Compliant System.
Choose Update Driver Software.
Heed the instructions onscreen.
Also try repeating these directions, but use the item titled Microsoft ACPI-Compliant Embedded Controller in Step 5. (Indeed, you can choose any item with ACPI in it if it seems to be the source of trouble, such as the ACPI Lid item when you’re having issues with the laptop not sleeping when you close the lid.)
If this method doesn’t work, you must visit the laptop manufacturer’s website. Search the Support section for your PC’s make and model for any new power management drivers.
Do not remove any ACPI entries, because doing so may disable some of your laptop’s power management features, such as the ability to sleep the laptop by pressing the Power button. It's a real pain to reinstall these features.