Intel Imac and mini dvi to hdmi setup

I have a 17" Imac 2.0 with a broken display. Evidently the person that I got it from made half on attempt to fix it, and then put it back together. The RAM wasn't seated correctly, so she wasn't even getting the startup chime. I reseated the RAM and got the chime. I had a mini dvi to hdmi connector laying around, so I attached and it plugged it in to my tv. Now, is there a way to force it to detect displays at startup? Or any other way anyone knows to get this to display externally?

Basically I am trying to see if the display is the only problem with the computer, before I buy one. I tried target disk mode to no avail.

If it was a notebook it could be done by using clamshell mode, however, with an iMac that's not possible. If you already tried Target Disk Mode and it didn't work, I don't know of another way to force the video to an external monitor.