I've had my iMac since 2007, and the 250Gb hard drive has just cashed in its chips (so to speak). I'm therefore upgrading to a 1T, and have decided to simultaneously up the shipped 1Gb RAM to 3Gb. I've read through the buying advice in MacRumors, and consequently searched on line. I've found DDR2 SO DIMMs described as 1.8V, 2.5V, or (the majority) without voltage requirements described. This isn't covered in the buying advice... Can anyone point me in the right direction? My new hard drive arrives today, and I'll be installing it at the weekend. It would be good to upgrade the RAM at the same time.