The conductance fluctuations for various types for two- and three-dimension
al disordered systems with hard wall and periodic boundary conditions are s
tudied, all the way from the ballistic (metallic) regime to the localized r
egime. It is shown that the universal conductance fluctuations (UCF) depend
on the boundary conditions. The same holds for the metal to insulator tran
sition. The conditions for observing the UCF are also given.