Lifehacker’s Whitson Gordon has some great tricks for getting into a computer without necessarily having the password and making sure that you keep it protected from anybody else doing the same.
The easiest is probably to use a Linux CD to access just the files you’re trying to get to:
How It Works: Just download the live .iso file for any Linux distribution (e.g. Ubuntu) and burn it to CD, then boot the computer up from that CD. Pick “Try Ubuntu” on the first menu – that should take you right into a desktop environment from which you can access most of the hard drive.
How to Beat It: Although this method can give you access to the file system, the malicious user still won’t be able to access any encrypted files. So if the owner of the PC has encrypted their files, the bad guy won’t get very far.
Click here for more clever tricks and to read the full article.