This great command line utility for Windows by Mark Russinovich over at SysInternals is the quick and easy way to get whois info for domain names or IP addresses.
Whois performs the registration record for the domain name or IP address that you specify.
whois domainname [whois.server]
whois IP address [whois.server]
Domainname can be either a DNS name (e.g. www.powercram.com) or IP address (e.g. 126.96.36.199).
For ease of use I prefer to save whois.exe to my Windows system directory (usually C:WindowsSystem32) which is already in your path so you can invoke whois from any directory in the command prompt.