You need a new graphics card.

Nvidia's high end models now are the 8800GTX and 9800GTX which both have versions with 1GB memory.

The downside is they run from $400 to $600 per card.

If you are interested in viewing your memory usage open the Task Manager / Performance / Physical Memory (K) / System Cache

That is the number being used.


You can also go to Administrator Tools / Performance

Here you can set your own parameters for testing and logging.

Jephree's right about "My point is over 2GB of RAM on a PC is probably never used."
I have 3GB, 512mb used for the onbaord graphics. This leaves me with roughly 2.5 GB. I can run os's in vmware and virtual pc, use programs like fireworks, and loads of video editing all in one session and my gadget in the sidebar with the speedos tells me I've used up 69% of my 2GB.
But extra RAM is nice to boast about your computer, especially since I bough 2x 1GB chips from crucial for £32 with free postage

I was hoping to speed up the PC but what would cause the freezing I get somewhat offten.

Depending on the motherboard you might be able to get Faster RAM. Depends on your FSB as well as possible overclocking options.

In other words get faster not more.

Freezing is often a hardware issue. Could be heat. Could be faulty RAM.

Running MemTest is always a good idea when problems persist.

MemTest
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Try running MemTest.

I had the freezing as well (vista) and upgrading the ram seemed to sort it out. (either that or my new mobo...)