Hi mustafakhan,
Welcome to the HP Forums! I saw your post looking for drivers for Windows 8.1. There are no specific drivers for your model available for Windows 8.1. It is going to be trial and error to find specific drivers.
Your particular product is a commercial unit to get your issue more exposure I would suggest posting it in the commercial forums. You can do this at http://h30499.www3.hp.com/hpeb/
The experts there will have additional resources and maybe able to find you specific drivers.
Thank you,