Windows Vista 32-Bit by default cannot detect more than 4 GB of RAM. Basically this limitation is set because 32 bit system always lose efficiency in managing memory. Here is a there’s a really technical explanation for this. However there is hack which will easily let you go beyond the limitation.

This is how it goes. Firstly click on the Start orb and in the search are type.

cmd

Don’t hit the enter key however. After a while cmd.exe will appear in the programs list. This hack only can be done if your are in Administrator mode. To do this, right click on it and choose Run as Administrator.

Once your command prompt is open, type:

BCDEdit /set PAE forceenable

To undo, just type “BCDEdit /deletevalue PAE” , this will remove the added PAE settings.

BCDEdit is a boot configuration editor for the command line. Using the above command you’ve just enabled Physical Address Extension (PAE) which can address memory larger than 4 GB. Now check your Device manger wow!…….now i got 4GB ram. But i have seen many users not able to do the workaround check this article at Microsoft on way it may not workout.