How can I prevent others from taking data off my computer?
Answer: Unfortunately, there really is no way to stop somebody from removing data from your computer via floppy, CD-R, USB drive, or other media. If somebody has access to your computer, there is no built-in security to prevent them from copying files to removable media and taking the data with them.
The best way to prevent people from taking data off your computer is to create a user account with a username and password. All the files stored within your account (such as the My Documents folder in Windows or the Home folder on the Mac) will only be accessible when you are logged in. Each time you leave your computer, log out, so that others will not be able to gain access to your files. You may even want to set your computer to log you out automatically if the system is idle for a certain amount time in case you forget.