We have a iMac 3.06GHz Intel Core 2 Duo (21.5-inch - DDR3) Late 2009 System with 8 GB RAM running Mountain Lion. My wife is a photographer and the primary user. She used a lot of Photoshop and Lightroom and always shoots in Raw. Her computer seems to be getting really slow. She does all her image selection in Lightroom. As she goes through her catalog of images she click to enlarge ones she likes to check for sharpness of the image. When she does this it will take her iMac 10-15 seconds to render the larger image. As you can imagine going through 300-500 images, even if you're only clicking on 100 or so of them can take a lot of time and be very frustrating if images are taking that long to load. Any thoughts on what could be causing this? She keeps most of here images on external drives. I try to keep her internal hard drive less than 75% full. She does end up with a lot of stuff (JPGs mostly) on her desktop for various reasons. Her catalog is on her hard drive. She had been working with her images on external drives. But we've been trying to speed things up by having her do her editing to images on her internal drive and then moving them to the external when she's done. But that hasn't helped much or at all. Any thoughts would be appreciated.