I'm looking to upgrade my iMac 20" 2.0GHz (bought November 2007) from 1GB to 4GB of RAM. I am looking at the OCW 4GB but it says PC-5300, and the Apple website says I need PC2-5300? What's the difference? Everything I read on here said people have bought the OCW 4GB and have had no problem, but is that the PC-5300 or PC2-5300. Maybe I am being stupid and can't find it on the website?! Also, will this void the warranty at all?