Visit http://www.auditmypc.com and you'll see your IP address, the information section gives you more detailed infomation about your system. It may even show you your internal address behind your firewall depending on how you're configured.
You can also drop to a CMD prompt and type IPCONFIG /all
How do I find out what my IP Address is? I have downloaded Microsoft Baseline Security Analyzer but I need to know my IP address to get it to work. Any ideas?