  We compare the effects of temperature, disorder and parallel magnetic field
on the metallic-like temperature dependence of the resistivity. We found a
similarity between the effects of disorder and parallel field: the parallel
field weakens the metallic-like conduction in high mobility samples and make it
similar to that for low-mobility samples. We found a smooth continuous effect
of the in-plane field on conduction, without any threshold. While conduction
remains non-activated, the parallel magnetic field restores the same
resistivity value as the high temperature does. This matching sets substantial
constraints on the choice of the theoretical models developed to explain the
mechanism of the metallic conduction and parallel field magnetoresistance in 2D
carrier systems. We demonstrate that the data for magneto- and temperature
dependence of the resistivity of Si-MOS samples in parallel field may be well
described by a simple model of the magnetic field dependent disorder.
