Look i can understand you are frustrated that everyone goes after you for your PC. Be it the cost or what not. But that is still no reason to break the rules. Sorry. He did not say anything all that bad. All he did was make a comment that you might not have a CPU that you state. Nothing that bad in that.
Now seriously please abide by the rules. You have bypassed the swear filter on your post above and that is technically another infraction and a week off. But i will give you a chance to calm down, edit the post and take a breath.
Now my question is this. Do you have a 32 Bit OS or 64 BIt? If it is 32 Bit that could be where you issues start. Since Vista 32 Bit does not play well with 4GB of RAM and that could be where your problems are starting.
The issue with Firefox i would say that the resources it is using are out of control. How many tabs do you have open? How much memory is it using? Have you tried to run the Firefox Optimizer app while running Firefox to see if it helps?