Put all the employees in a locked room with a revolver with a single round in it on the table. Tell them that if the pirate in question is not dead in 10 minutes you will release sarin gas into the room. Might want to clear it with management first, though.
There are companies out there that are like vultures, they wait for the smell of pirated software coming from a small business and then they attack. So button that shit up quickly! I worked at a place that got audited and it suuuuuuuucked, you practically need a DNA sample from the salesman you bought the software from to…
He's not a real network admin. At least that's what I gathered by "teh unofficial IT guy". Use scare tactics and remind people that pirating at work will lead to dismissal. If they don't just want it to stop, but want to use it as an excuse to fire someone. Anyone. Then I'll just say "tough luck" and let someone else help…