  The paper is withdrawn by the author. Parts of the contents are expanded into
separate papers; hep-th/0308015 LOCALIZED TACHYON MASS AND A G-THEOREM
ANALOGUE, hep-th/0308028 COMMENTS ON THE FATE OF UNSTABLE ORBIFOLDS,
hep-th/0308029 CHIRAL RINGS AND GSO PROJECTION IN ORBIFOLDS.
