Is there any way I can get access to the rest of my memory?

[Graham Watkins]

Hi folks,

I've just installed 12.04 + Mate.  At the same time I upped my memory to 
4gb. I already knew that my 32 bit system wouldn't recognise all of it 
but I was somewhat disappointed to find that only 2.9gb showed up.

A bit of googling suggested that installing the PAE kernel would make 
more memory accessible.  This I have done but it hasn't made any difference.

I know that I should get the full memory if I install the 64 bit version 
but, if I have understood correctly, this would use twice as much memory 
anyway, giving me equivalent to 2gb on a 32 bit system, so I don't 
really see the point.

Is there anything else I can do to get my system to access more of its 
memory, or am I stuck with this?

Cheers,

Graham