Intel iMac as an external monitor - Guide
I had a 2006 Intel iMac that died (logic board / graphics card failure) and instead of consigning it to the bin, I aimed to turn it both an external monitor for my screen-less 2009 MacBook Pro (LCD driver failure, failing battery) and any HDMI device I wanted. I had seen this done with G5 iMacs, but never with Intel ones, which use different display types, so decided to have a go and was successful!
My guide can be found in the answer...
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