[Help Recognising All My RAM]

Hi

I have 6gb of ram instaled and i am only able to use 2gb

I have

2x amd optiron x64

6gb ram

A 64x motherboard ... I cannot remember the chipset name

All 6gb is recognised by bios but not windows

I havent a clue what to do my mate says pae wont work as i have amd processors but i think different, there has to be a way i just cant find it.

So any help will be appeciated

Cheers

Ant