I just successfully replaced my dead hard drive with a WD Caviar Green drive in ~4 hours (minus a trip to Ace for a narrower T10 driver), despite being terrified. As a novice, this was difficult, especially removing the front bezel. That took me 30 minutes of trials. I had to use a lot of force in removing that and the hard drive. A couple of times my computer differed from the guide (I have a 2 GHz intel core 2 duo white imac). For instance, my hard drive temperature sensor looked completely different and wasn't labeled, and some other connections were in completely different places than in the demo, so I had to hunt around. I also think I messed up the hard drive thermal sensor when I put it on the new drive because my fan was running at high speed after this, like Andrew describes above. I downloaded hddfancontrol and that instantly fixed it. It took 10 seconds to install and then the fan noise stopped. Regardless, the guide was great-I had no business even trying this but it worked!