MultiCharts database files are located here X:\Documents and Settings\All Users\Application Data\TS Support\MultiCharts\Databases\ directory, where X: is the drive where MultiCharts is installed (C: by default):

X:\Documents and Settings\All Users\Application Data\TS Support\MultiCharts\Databases\FBPORTFOLIO.GDB
X:\Documents and Settings\All Users\Application Data\TS Support\MultiCharts\Databases\TSSTORAGE.GDB
X:\Documents and Settings\All Users\Application Data\TS Support\MultiCharts\Databases\TSCACHE.GDB

Note. The files from different "Databases" directories should never be mixed.