if i were to do it my self, i have an AIO desktop but its basically a laptop so should i use laptop components in it or try and find my specific brand? i have a AIO 300A HP Desktop >.> if it pops up as a printer there just switch around the words sorry there's a printer that they have with the same model name.
If you are trying to RECORD HDMI, copy protection will stop you. So even external cards to allow recording of HDMI will not work with any set top boxes and what not. They do work with video cameras and stuff.
If you just want to use it as a screen, HP would have had to give you access to an input when they built it. Unfortunately, they did not.
While with some work, you MAY be able to track the video signal to the MB(inside the screen) and make an adapter(lets say use an HDMI switch to select PC or input), it would generally be more difficult and is not for beginners.