Can you use a 2009 21.5 inch IMac as a Windows PC second monitor

I've got this 21.5 inch IMac from 2009~, but recently have wanted to use it as a second monitor for my Windows PC. My graphics card has a Displayport, but no mini, so I was wondering if the IMac would even work as I intend to use it before I went out and got a Mini Displayport to Displayport adapter.

Thanks in advanced, Chef Head.