I have a 2008 24" iMac.2.8 GHz with 4 GB RAM. My hard drive failed about a year ago and Apple replaced it. I am running SL, but see the rainbow beachball every day. I would like to upgrade to ML and to stop the beachball. I am thinking I may need to upgrade my RAM to 6 GB. I ran the activity monitor and it shows I am using a lot of RAM. I searched the forums but can't find the link to a website that will help you determine exactly what kind of RAM you need. Can anyone post that link? Any other advice? I am thinking of upgrading to a new iMac next year, but I would like to salvage this one so my kids can use it. Thanks for any help.