According to your description, I suggest you refer to the following information:
Please use FN+F2/F3 to see if you can reduce or increase the screen brightness. If you can't adjust, you can refer to the following suggestions:
1. Please recall whether this phenomenon occurred after some special operations. For example, please check whether third-party optimization software is installed in your computer. If so, please check whether the screen brightness level function is disabled in the optimization software. Please enable it.
2. If you don't have any startup items to set, I suggest you disable startup items and services. Method: Please click on the Start menu, enter msconfig during operation, open the system configuration, disable it all in the startup item, then hide all Microsoft services in the service, and then disable it all.
After this operation, you can test whether the brightness of the screen can be adjusted normally, in case one of the startup items you installed before disables the brightness level function.
3. This situation may also be caused by a problem with the graphics card driver or the shortcut key driver. I suggest you reinstall these two drivers. The driver download address of HP official website's 4446S notebook is as follows:
& ampcc = cn & exchange admission =1351920209829+099480143.
4. If the above methods can't solve your problem, I suggest you try to restore the BIOS default value after warranty data. These methods are as follows:
Click F 10 to enter the BIOS, select Retreat Defaults in the file, click yes, and then select Save Changes And Exit to save and exit.
5. Tips: The little moon icon is in the key position of F 1, and the function of FN+F 1 is to start the sleep mode, not to adjust the screen brightness.
I hope the above reply can help you.
If the above information can't solve your problem, you can log on to www.hp.com.cn/chat,, the online chat room of HP Network, and ask an online engineer to help you solve the problem further. More product information is available in www.hp.com.cn/800..