Reverse DNS

I work for a school district and our addresses are all kershaw.k12.sc.us I would like to be able to download the 128 bit encryption versions of NT SP's but I cant cause they can't do a reverse DNS lookup on us. It simply resolves our IP address to our IP address which is 207.232.137.3 I thought I knew how to do the PTR record in DNS but it says it can't do it. I am guessing it is because we are not top level domain name. Am I right or is there a way around it? Thanks.

two things I have to ask. Who assigned the Machine name. and are you running your own DNS. If not, You could solve your problem by running your own DNS server, pointing it to the Main DNS server for the ISP that you use. Then you can setup your own PTR records.