Hi, I've been a Mac user since the iMac G5s were released however I still don't really know much about OSX. Since about 10.4.3 (I think) my iMac started getting slower and the fans were making constant noise. However after reading here a bit I noticed that "Repair Disk Permissions" was thrown about a bit, so I decided to try it last night and noticed the CPU usage and fan noise was drastically reduced (fans make virtually no noise unless I really push it hard) and system speed was improved. Now my question is, how did it make the iMac suddenly faster? Is it like defragmentation on Windows or something completely different? If possible I'd like a slightly more technical answer as I'm studying to be a Computer Systems Engineer so this kind of thing should help me in the future. Also is there any other things I should perform to keep my Mac at peak performance?