Connecting Laptop to PC

Hi,
So I'm entirely useless when it comes to computers, cables, ports, etc. so any advice and help is much appreciated.
I have been previously able to connect my Laptop to a TV via a HDMI cable to make the TV basically act as the monitor. I now want to connect my Laptop to my PC to make the PC act as the monitor, however my PC is an all-in-one and doesn't have any visible HDMI port. All I can find on my PC, other than an excessive amount of USB ports, is a strange port about as tall as two USB ports with a symbol above it that looks like a line with three boxes along it. Sort of like:
[]
___
[] []

But more compressed than formatting here allows. My Laptop runs Windows 8 and my PC windows 7.
How can I connect the two?
Any/all advice or help is welcomed!
 
Check the manual which came with the All-in-One. Failing that, check manufacturer's website for downloadable manual.

Chances are unlikely that you can connect from laptop to AiO as most AiOs are not intended to be used as monitors.
 
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