On a 32-bit system, no single app can use more than 2GB of RAM (if I understand correctly). So
3GB won't help very much. This is a particular pain, because even when running a
memory-monitor on the taskbar, you can't easily see whether one particular app is about to run
out of addressable RAM.
That's why my new desktop machine is 64-bit, so that firefox can address almost 8GB of real
RAM, and furthermore, leak into 16GB of swap, before it finally crashes!