Hi guys: One of my systems is a 2009 mid year MacBook and the drive that came with it is going. I started getting the spinning beach ball syndrome on it along with messages like "not able to open file" and in some cases, I/O errors. I used Scannerz sometime ago to check an external drive, so I ran it on this one and it's diagnostics mode confirmed that it's the drive, not an internal cable or some other system problem. This came on suddenly. To the best of my knowledge the unit wasn't dropped or anything, but I do have kids, so who knows. I use this thing basically to do less critical work, but with drive prices being so cheap I was considering using either 500GB or a 1TB 7200RPM Hitachi drive. I use Scannerz about once a month to check the health of drives on my systems and one thing that I noticed, but didn't really surprise me, was the fact that it scans 7200 RPM drives faster than 5400RPM drives. I'd really like, but don't need to get the 7200RPM drive. I can easily get by with another 5400RPM drive, but I'd rather not considering the fact that the 5400RPM models are only tens of dollars cheaper. My question is about heat. One thing I don't like is to have the fans come on and my assumption is that the 7200RPM drive will use more power. However, will it leave my system in a state where the fans are running either all the time or very frequently. You can get the tech specs for the drives I'm considering here: http://www.hgst.com/hard-drives/internal-drive-kits/mobile-drive-kits I'm not interested in SSDs because of their cost and limited storage for the money. The system has 4GB of memory and has been running Mavericks just fine. I'd like to add that this has been a remarkably good computer, just because it's the truth. I haven't had any problems at all with it until now, and it's the drive, not anything more complicated.