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We present here the recent progress in our understanding of the old stellar components of the Milky Way as fossil records of galaxy formation. Special attention will be paid to if the Cold Dark Matter (CDM) theory as a current theoretical paradigm is able to reproduce recently accumulated data sets of Galactic stars as provided by extensive surveys such as SDSS. We show our recent studies in this regard. First, we have simulated the dynamical interaction between a stellar disk and numerous CDM subhalos to get insights into the origin of the thin and thick disks. Second, we have analyzed the global dynamics of more than 1600 field horizontal branch stars as halo tracers to probe their velocity distribution inside the dark halo of the Milky Way. A detailed comparison with the CDM predictions has been made and key issues are addressed for understanding the formation of the Milky Way. [ABSTRACT FROM AUTHOR]

We briefly describe the kinematics of about 1200 metal-deficient stars in the solar neighborhood, based on the recently completed catalog selected without kinematic bias. We stress here that the stellar halo possesses internal subcomponents characterized by different kinematics and density distribution. The implications of the current data for the formation of the Galaxy are also discussed. [ABSTRACT FROM AUTHOR]

We numerically investigate whether the CDM model can reproduce reasonably well chemical, kinematical, and structural properties of the Galactic stellar halo. [ABSTRACT FROM AUTHOR]