I saw a domain name which has no available WHOIS information. Is it possible to register a domain name and hiding it's WHOIS? Where and how? Thank you!
If they are not registered on who is then they are usually registered on another database, and the whois data base usually tell you what database to look them up on What did whois say?
Private Registrations will show WHOIS, but not your info -- in case that is what you are looking for. If it is just about there bring NO whois, I think it is a database issue and should self-rectify.
Most registrars offer private registrations from being free (Namecheap) to a few bucks per year per domain.
It depends of which TLD you are addressing. For example, .to (Tonga) registrations may hold the registrant's data completely hidden.
http://www.godaddy.com gives you the possibility to add private registration for a small additionally fee.