The Nslookup command in windows 7 can be used to convert an IP address into URL or a web URL into an IP address. You can use this command-line utility 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.

There are few other tools like dnsstuff.com, which offers an impressive collection of online tools for looking up domains, IP addresses, and host names. via Technet