Hi 11736,
Thank you for visiting the HP Support Forums and Welcome. I have read your thread on your HP Wi-Fi Direct Mobile Mouse and concerns being compatible with Windows 8.1. Shows me that there are no drivers available for Windows 8.1 but you could try to run in compatibility mode. Here is a document on how to do that from Microsoft.
The HP Support Assistant could check to make sure the drivers are installed correctly. Here is a link on how to use the HP Support Assistant.
Hope this helps you.
Thanks.