I agree with this work your 40 hours period. He will either comply and your life will get better or fire you. Seems like a win-win for you.

The question here is are you getting college credits for the internship, and if so what are the details. Our local community college has internships you get college credits for, and it is stated in the fine print how many hours your committing to. After that commitment is met you may leave at any time. However, I don't know if any of this applies to you.

I have to agree with @FreeMan. I work in IT and knowing column names was expected of me in 20 years, if they existed I would have just looked them up and no one would have cared. If you were'nt leaving I would go and ask point blank, why know this information is expected and were this expectation was previously mentioned. Further, I would ask would you rather have someone who's made a few mistake and learned from them, or start over and have someone else make those mistakes and possibly more.

Under what conditions did it used to work? You had windows 7 and it worked before? Maybe you can make a virtual machine and create the working environment until the actual problem can be resolved?

Your at a trade show, what do all the other vendors do? Did they hire someone? Contract with the trade show host? Ask around.

If your the manager is there a reason you didn't hire a hostess or an outside vendor? Sales people are there to generate revenue for your company, if they are dealing with potential clients then cleanup isn't necessarily there job. If taking time to cleanup costs your company $10,000 in sales that is a bad choice. Hire a temporary worker.