I was getting ready to buy some memory for my flatscreen iMac and read this in the installation instructions: 'Turn your computer off by choosing Shut Down from the Apple menu. Unplug all cables, except the power cord, from your computer.' Is this right? Does it mean unplug from wall, but leave the cord in the computer back? Does it mean leave plugged into wall? Later it says to unplug the cord from the computer but only after you unscrew the bottom of the computer and touch metal. Sorry, but this goes against everything I have ever known about electronics...unplug first, then unscrew! Help please.