Open an DOS windows and execute the following script.
nslookup -type=ptr xxx.xxx.xxx.xxx
C:\Documents and Settings\username>nslookup -type=ptr 208.74.137.66 Non-authoritative answer: 66.137.74.208.in-addr.arpa canonical name = 66.64-95.137.74.208.in-addr.arpa 66.64-95.137.74.208.in-addr.arpa name = dbm0000.shared-servers.com 64-95.137.74.208.in-addr.arpa nameserver = ns3.databasemart.net 64-95.137.74.208.in-addr.arpa nameserver = ns4.databasemart.net ns4.databasemart.net internet address = 65.99.254.78 ns3.databasemart.net internet address = 208.74.136.73