ERROR: Unable to handle this request. HTTP ERROR 500

I think this would be a little bit overkill. But have a look first which webserver was actually running (lighttpd vs. Apache) and also check if there are any leftovers of old configs with references to oC left.

Not sure about that. You don't what the previous admin did. A new install you know at least that there is nothing broken from a previous setup. But it is some work to do especially for a beginner.

Thank you very much for your help guys and apology for such a delayed reply. I end up reinstalling the whole server. It seemed easier.