I have got the 2.4ghz aluminium macbook, and I upgraded the ram to 4GB about a 2 months back. I have always felt that my macbook is slower now than before the upgrade(which is strange), but recently the situation became worst. My macbook would randomly heats up very quickly, iStats pro would show me that i only have 1-10MB of free memory, my fan would be running on 6200rpm. response rate would be much slower, and circle of rainbow also occurs much more often.. I get panic whenever this happens(i have only got my macbook for 5-months), so when that happens i usually try to quit those application that i am not using like mail, safari, iwork 09 and etc. It didn't really help much(or maybe not at all) until at some point(around about 30-45mins) the systems automatically cools down, reduce fan speed and etc but similar problem would happen again in 30mins. it's true i have more applications now, more background apps, and more plug-ins as well but they shouldn't be taking too much of my memory. I am really afraid that my macbook might probably got affected by a virus or some sort(i came from a windows background). I have tried reading stuff on ram, paging in, out, cpu but most of them are too technical so i couldn't get much out of it. What i really want to know now is; 1) what's responsible for the heat increased in my macbook? the cpu usage? the ram? or?? 2) why when i quit some applications, my free memory doesn't free up? 3) am i running too many applications? is the background applications taking up too many spaces? 4) is virtual memory more important than real memory or via versa? 5) Should i delete applications that i don't use often? 6) What can i do? 7) What's happening to my macbook? Please let me know if i have missed something, or if there's something i am not aware of, or if you need more screenshot pictures. thank you very much now, I would appreciate any help..