I have a list of IP addresses in a text document (ip.txt).  I would like to
export that list or paste it into a program that will perform reverse
DNS on it and give me a list of domain names related to the IP
addresses.  This program needs to run in MS windows.  I need it to be
a free or <$30.

As per a previous googleanswer
(http://answers.google.com/answers/threadview?id=314958), I tried
QDNS, but I could not figure it out.  I have a file "ip.txt" that has
3 ips listed as (example):

xxx.xx.xxxx
yyy.yy.yyyy
zzz.zz.zzzz

and I have a file in the same folder "results.txt"

So... what command line do I type to have the IPs from "ip.txt" be
listed in results.txt as:

dje33.michigan.edu
server.aol.com
joey63.verizon.net

Alternatively, if it exists, is there a simple GUI program (i.e.
non-command line) that does this for me?  Do I need to know a DNS
server to use to look things up (I don't know how to find one).  Help!

You may like the following freeware program:

FastResolver http://www.softpedia.com/progDownload/FastResolver-Download-27918.html

I'm not sure how it works though when the IP address has multiple
names associated with it.

You will need a DNS server but just about any meaningful connection to
the Internet will have a default primary and secondary DNS server for
you to use to do the lookups. In other words, if you can view this
page, your connection has access to a DNS server to use. However, if
the list is long, please be responsible and do the lookups in the
middle of the night or some other non-peak time.

thanks so much!  that was exactly what i was looking for!