I was given my mother’s iMac after she passed away, but I don’t know the password. How can I gain access to this Mac?
Via the internet

This question is a little delicate because you could use the method we’re about to describe to access any Mac. But situations such as yours (as well as problems that come up when you purchase a used Mac that hasn’t been properly cleared) invite a response – and we know our readers would never use the information given here for evil.

Locate that Mac’s installer disc or a recent OS X installer disc – for example, an OS X 10.4 (Tiger) or OS X 10.5 (Leopard) disc. Insert that disc into the Mac’s media drive and hold down the keyboard’s C key to start up the Mac from that disc.

When the Mac boots, you’ll be asked to choose a language. Do that and then click on the right-pointing arrow icon to continue. When the Welcome screen appears, wait for the menu bar to materialise and choose Utilities?Reset Password. In the resulting window, click on the Select A User pop-up menu and then choose the user whose password you want to change. Enter and confirm a password in the appropriate fields and, if you like, enter a hint for the password. Click on Save to make the change.

“Oh, great,” I hear parents saying. “You’ve just given my kid the key to taking over my Mac. Thanks so much!” Fortunately, now that you know how to break in to your Mac, you can make it more difficult to do so.

Boot your Mac from that installer disc again, find your way to the Welcome screen, and choose Utilities?Firmware Password Utility. In the window that appears, click on Change, and then enable the Require Password To Change Firmware Settings option and enter and verify a password. Click on OK, and your Mac is now protected with a firmware password.

This means that if your kid starts up your Mac with an installer disc in the media drive and presses the C key to boot from the disc, the Mac will ignore that key press and move to the login screen. If the kid is really savvy and presses the alt key to move to the screen where you choose a device to boot from, a padlock icon will appear with a text field below it. If your child fails to enter the correct firmware password in that text field, the Mac will not boot from the disc.