Get IP Address Information with IPNetInfo
IPNetInfo is a small utility which allows you to find all the information about a given IP address such as the owner of the address, the country/state, contact information, address range and much more. You can even check multiple addresses at the same time and convert host names if the IP Address is not available to you.
The IP Address information is retrieved by sending a request to the whois server of ARIN. If the information is not there, another request is sent to the whois server of RIPE, APNIC and LACNIC. After the information is returned, it is displayed by the software in the form of tables. You can even paste email headers directly into it and it will extract all the IP Addresses from it and display all the information. This way you can find more about the origin of the email.
It is a freeware and works on Windows 98/ME/2000/XP/2003/Vista.