I have a late 2007 iMac 2.4 Intel Core 2 Duo with 4GB ram in it. I have a 500GB HD with 130GB free and I am running Mavericks on it. I have gone through several of the "how to speed up your mac" threads and have barely anything that starts up when the iMac is booted up. I have run the ONYX program and repaired all the permissions and all of the other things that it does. Rebooted the iMac to clear the RAM.. I don't know what else to do. This thing beachballs and takes FOREVER to open up almost any program. I run "Freememory" to make sure I am not running the RAM into the ground and even when I have 1.5GB of free RAM it still runs slow. This thing ran WAAAY faster with Snow Leopard on it. I just don't think Apple should have even allowed my machine to be upgraded to Mavericks if they knew it was going to run this slow. It is really an embarrassment. I am not able to purchase a new iMac at this time so I am stuck with what I have. I almost wish I never upgraded to Mavericks.