We present a consistent model of storage, instability and dynamical eruption of magnetic flux tubes in the solar convection zone and underlying overshoot region. Using a convection zone model with self-consistent overshoot layer, we calculate equilibrium configurations of magnetic flux tubes and determine their linear stability properties, taking into consideration the effects of stratification and rotation. Instability of flux tubes stored in the overshoot layer with growth times below one year requires field strengths of the order of 105 G; in many cases, the dominant mode has an azimuthal wave number of m = 2. Numerical simulations are used to follow the nonlinear evolution of such unstable flux tubes and their rise through the convection zone, from which they emerge to form active regions. The results are in accordance with the following two requirements, based on observational facts: (a) the upward motion of the tubes is not significantly deflected by the Coriolis force so that they can emerge at low latitudes, (b) their inclination with respect to the East-West direction (tilt angle) as a function of the latitude of emergence is consistent with observations of acitve regions.