Look up memory management and about:config on goole.
There are about four very helpful howto's catered to Windows' users.
I am using Firefox 3.5.3 on an older Dell desktop PC running Windows XP operating system with 2.5 meg RAM.
Of late, the Firefox keeps crashing. It stops operating and when I bring up task manager, I notice that it shows 100% utilization of CPU. I would suspect my installation, except I am getting the same problem on my much newer laptop also running XP with 2 meg RAM.
The one thing in common between the two computers, except the operating system is that I am using Norton Internet Security 2009 in both machines.
Is anybody else experiencing similar problems? Or is my problem related to something other than Firefox?