Apple has started a replacement program for a “very small number” of Seagate 1 TB hard drives that may fail in certain conditions. These drives came in 21.5-inch and 27-inch iMacs sold between May 2011 and July 2011. Although Apple is contacting iMac purchasers who provided a valid email address during the product registration process, you can also enter your iMac’s serial number on this page to see if it’s included in the replacement program. As always, back up your data regularly, and be certain to run a backup right before you take your Mac in for the replacement so you can restore onto the new drive. follow link
Option-Click AirPort Menu for Network Details
If you hold down the Option key while clicking the AirPort menu in Mac OS X 10.5 Leopard, you'll see not just the names of nearby Wi-Fi networks, but additional details about the selected network. Details include the MAC address of the network, the channel used by the base station, the signal strength (a negative number; the closer to zero it is, the stronger the signal), and the transmit rate in megabits per second showing actual network throughput. If you hover the cursor over the name of a network to which you're not connected, a little yellow pop-up shows the signal strength and type of encryption.
Apple Replacing Some 1 TB iMac Hard Drives