I've booked to go to New York with a friend on November 13th. The problem is my friend might have a criminal record for a minor offence almost 10 years ago. It is too late now to get a visa and my 5 day trip is non refundable. Should I be worried that my friend will be denied entry?
"Might" have a criminal record? My guess is a visa is needed if there really is a criminal record. I presume you are from one of the countries which do not require a visa to enter the US. First, confirm with the police to see if there really is a record. If there is, contact the US Embassy in your country and explain to them about the situation. They're the best people to talk to about this and will advise whether or not your friend needs to apply for a visa. Anyway, November is more than two months away, so there's still time to apply for a visa if it's required.
I'm guessing from your thread from 17 hours ago that you haven't done as Sander suggested and made contact with the US Embassy then?