The Nslookup command is a buried treasure in Windows. You can use this command-line util¬ity to quickly convert a fully qualified domain name to its IP address. You can tack on a host name to the end of the command line to identify a single address. For example, type nslookup ftp.microsoft.com to look up the IP address of the Microsoft File Transfer Protocol (FTP) server.
Or type nslookup to switch into interactive mode. From this prompt, you can enter any domain name to find its IP address.
If you need more sophisticated lookup tools, you can find them with the help of any search engine. A good starting point is dnsstuff.com, which offers an impressive collection of online tools for looking up domains, IP addresses, and host names. The site also offers form-based utilities that can translate obfuscated URLs and dotted IP addresses, both of which are widely used by spammers to cover their online tracks.