Seriously! I may sound harsh but why are we even allowing these threads outside of 'newbie'? You don't know that x86 Windows can't address more than 3.8 GB of ram, and you are asking cryptocoin mining questions. Seriously. ALL of this could be answered better with a single Google search.
Well if you don't know what's wrong to begin with then google won't help at all. It's also not just x86 windows. It's any 32bit operating system.
Three letters. PAE. 32 bit OSs are NOT limited to 4GB of RAM... God, people.