I have iMac i7 2.8/8GB and 150Gb used on a 1TB. Ive notice a slight performance lag on my computer. I have done repair permission and rebooted my computer. For some reason this week I have notice off sluggish behaviour or contant noise from HD doing something. Some times when I right click something the window takes a long time to pop up. (reboot fixes this), and other times scrolling pages on a website lags. I took a picture of the activity monitor. In the pic, I only have outlook open and nothing else. You can see some random stuff is being written to the HD. No idea what it is but it jsut comes and I can hear it. Sometimes more frequent than others. It seems to buildup after a while and gets worst the longer the computer is on. I can hear the HD doing somethign while I am not really doing anything. You can see from the attached pic the red peaks.. on the HD. Most of the times the peaks are more frequent but constant. Anyone?