I have a problem with my Dell XPS One 27 (2710) all-in-one. I cannot get my HDMI output working (tried all devices: TVs, monitors, projectors etc. with many HDMI cables). I checked everything and it seems to be software conflict between Nvidia GeForce and integrated Intel HD graphic cards.
Anyone had any similar issues and how did you managed to solve them?
What operating system are you using? Be sure that you are connecting to #3 out, and not #4 in.
The external devices must be on and set to receive the HDMI in signal before you connect the HDMI cable to the #3 out port. Did you open both the Intel and Nvidia control panel and search for enabling the HDMI out?