I have seen this annoying problem in several Windows 8 (or 8.1) laptops when performing a computer shutdown: the screen becomes black, but the Processor (CPU) fan stays On and, in some laptops, the power state and Hard disk lights also stay on. During this behavior, the only way to fully shutdown the laptop is to press continuously the power button.
In order to resolve the above problem (fans keep running when Windows shutdown), I have applied the following solutions in separate occasions (different computers) with successful results.
How to solve: Fans keep working after Windows shutdown.
Solution 1. Enable Hybrid Sleep.
Hybrid Sleep feature is introduced with Windows Vista and combines the Sleep & Hibernate features. In simple words, when you enable the Hybrid Sleep feature, then Windows write active data on your hard drive (as hibernation does), but also provides low level power in your RAM in order to also keep there the active data (like Sleep does). To enable Hybrid Sleep:
1. Open Windows Control Panel. To do that:
2. Change the “View By” option to “Small icons” and then click “Power Options”.
3. Click “Change plan settings” at the active (selected) plan.
4. Click “Change advanced power settings”.
5. When Power Options appear on your screen, expand Sleep Settings.
6. Expand Allow Hybrid Sleep* option and set the "On Battery" and the "Plugged In" options to On and press OK.
* Notice: If Allow Hybrid Sleep option is missing, then:
a. Enable hibernation from the command prompt by using this command: powercfg.exe –h
b. Set the Suspend to RAM (S3) mode in BIOS. (See Solution 2 bellow on how to do that).
Solution 2. Set Power State (in BIOS) to ACPI S3 Mode (Suspend to RAM).
1. Enter BIOS settings and under Power Management menu, set the ACPI Suspend Mode (or Standby Mode) to "S3 (STR)".
2. Save and Exit from Bios Settings and log on normally to Windows.
Notice: If ACPI S3 mode is not available in BIOS settings, then you have to update the BIOS to its latest version. But, since updating the BIOS is risky, make sure first that the new BIOS version supports the ACPI S3 mode before updating.
Solution 3: Disable Fast Startup (Windows 8).
Try to disable the Fast Startup feature. To disable Fast Startup follow the steps in this article:
Solution 4: Disconnect Wireless Printers.
If you use a Wireless printer then switch the connection to your printer from WLAN to LAN (if that is supported by the printer). As a temporary solution you can also turn off your printer before shutting down your computer.
Other things to try if the above solutions don't work:
1. Disconnect all External Devices (e.g. Card Reader, Mouse, Printer, etc.)
2. Remove all unwanted programs that are running at Windows Startup. Maybe some of them prevent your system from going to sleep (like UTorrent, Skype, etc.). A free, easy to use and reliable utility to manage startup programs is the CCleaner.
Detailed instructions on how to to manage startup programs using CCleaner can be found here.
3. Install the latest drivers for your hardware (e.g. Graphics Card, Card Reader, USB, etc.).
4. If you own an HP (or other brand) laptop with a a switchable graphics feature (a laptop that have two graphics adapters) then using BIOS settings, set the Switchable Graphic Mode setting to Fixed. Detailed instructions on how to do that you can find here: Enabling Fixed Mode Switchable Graphics in the BIOS