I have had my 2011 27" iMac stolen last year and only just got it back from the police with the screen cracked . Since it was stolen I have been using a 17" MBP, and then upgraded to the 15 rMBP. The difference in speed between the regular hard drive in the 17" and the SSD was incredible. Now when I went back to the hard drive in my iMac, it seems so slow. Since the screen is cracked, I thought that I may as well install the SSD while I am replacing the screen. I only really use around 300GB of space, so have bought a 512GB SSD. I have heard that when replacing the iMac HDD, the fans run on full because of the temp sensor. Has this happened to anybody on here? How can I fix if it does happen? Anybody have any other tips on swapping the hard drive for SSD?