Mac OS X’s built-in parental controls allow you to lock the Dock and restrict other parts of your Mac too.

My mom just bought her very first iMac, and she loves it! However, she keeps accidentally pulling her icons out of the Dock. Is there any way that I can lock the Dock?

One way is to use Mac OS X’s built-in Parental Controls to prevent your mom from modifying the Dock, but in order to do this, you would need to change her account from an administrator account to a standard account in System Preferences > Accounts. Go there, click your mom’s account name, and uncheck the box that says, “Allow user to administer this computer.” (If it doesn’t let you uncheck the box, you need to create another account that has administrator privileges.) Then click the Open Parental Controls button, select your mom’s account name in the list on the left, and uncheck the box that says Can Modify The Dock.

Alternatively, you can leave your mom’s account as an administrator account and simply type this command into the Terminal: defaults write com.apple.dock contents-immutable -bool true

Log out and log in for your changes to take effect. To unlock the Dock again, substitute false for true.

If you’d rather use a GUI interface, many utilities come with an option to lock the Dock, including Cocktail ($14.95, www.maintain.se) and TransparentDock ($8, www.freerangemac.com).