cpu instructions... that means the machine code and also not the data i think?

i haven't yet noticed any 64bit applications using 40% more ram than their 32bit counterparts.

64bit windows makes a difference for me because of the 2gb per process and 3gb in total limit of 32bit windows. for example 64bit blender can use 3.5gb ram or so on my pc.

and once i upgrade to 8gb i won't have to install a new windows.