How to upcycle a 10-year old iMac (display)? There’s a lot of close-to-duplicate questions around here asking how to connect some computer (often laptop) with an iMac to reuse its larger display as a second monitor. Depending on the ports available and exact model number, there are frequently cited solutions like Target Display Mode, VNC Screen Sharing, Remote Desktop, Screen Recycler, Air Display or Air Play. They all require the iMac to run an operating system, though. 
What if some component of the old iMac (32-bit Intel model from 2006, limited to OS X 10.6.8) was broken, say the hard drive, so it won’t boot up and it would be okay to take it apart. 

I'd like to keep at least the display, power supply and casing, maybe solder on some connectors or add some alternate cables, which shouldn’t cost too much. Anything else could stay inside unless it needlessly consumed energy.

What would it take to reclaim the still functioning display?
There is an I Fix It Guide which describes the steps and hardware necessary. @Allan is right, though, in that it may not be worth it except for the fun of fixing stuff. This first Intel iMac can also be ugraded to a 64bit CPU with 4 GB of RAM and a SSD without a lot of efforts or costs.