Hi NX01,
I understand you have updated your computer to Windows 8.1. HP has not tested your system and Windows 8.1 and does not list drivers, but here is a document on Connecting a Monitor, Projector or TV (Windows 8). HP has no posted drivers for Windows 8.1 and this computer. Here is a link to a document on Downloading or Updating Software and Drivers for HP Computers. Have you done all your Windows updates? The Hp support Assistant will only look for HP updates and as I stated previously HP does not have Windows 8.1 drivers for your system.
