Like I said many forums say otherwise, here is a blurb:
So, before you go ahead and make your iMac as a monitor for your PC, you have to make sure that you check or have the following.
The very first thing that you would be needing to see is that if your iMac is compatible to use as a second monitor. You have to check on the ports of your iMac. And if it comes with a Thunderbolt or a Mini Display Port feature, then it means that you can use it as your second monitor. But on the other hand, things may not fall on what you are expecting. So with that, you have to check for their compatibility.
- If you have a late 2009 or a mid-2010 and a 27 inches in size that comes with a Mini Port Display port.
- If you have a 2011 and a 2014 iMac that comes with a Thunderbolt port.
Aside from that, there are also some late 2014 models that you can use as a second monitor. But, when it comes to the late 2014 5k retina iMac, it does not come with a Target Display Mode. And for the other things that you need as a requirement, you have to make sure that you have a PC that comes with a Mini Display Port or a Thunderbolt port.