diff --git a/twander.py b/twander.py
index c1bd473..9bdd035 100755
--- a/twander.py
+++ b/twander.py
@@ -6,7 +6,7 @@
 # Program Information
 
 PROGNAME = "twander"
-RCSID    = "$Id: twander.py,v 3.113 2003/02/28 20:05:18 tundra Exp $"
+RCSID    = "$Id: twander.py,v 3.114 2003/02/28 23:18:55 tundra Exp $"
 VERSION  = RCSID.split()[2]
 
 # Copyright Information
@@ -304,6 +304,7 @@
 SHOWDRIVES    = '\\\\'          # Logical directory name for Win32 Drive Lists
 STRICTMATCH   = CMDESCAPE       # Tells wildcard system to enforce strict matching
 
+
 # Sort Field Names
 
 fNONE        = "None"
@@ -509,7 +510,7 @@
 
 
 #####
-# Configuration File-Related Constants
+# Configuration File-Related Constants & Globals
 #####
 
 ASSIGN     = "="               # Assignment for variable definitions
@@ -518,6 +519,19 @@
 ENVVBL     = r'$'              # Symbol denoting an environment variable
 
 
+# Names Of Conditional And Pre-Defined Symbols
+
+CONDENDIF    = '.ENDIF'
+CONDEQUAL    = '=='
+CONDIF       = '.IF'
+SYMOS        = '.OS'
+SYMPLATFORM  = '.PLATFORM'
+
+# Globals Supporting Configutration File Conditional Processing
+
+ConditionalStack  = []         # Stack for tracking conditional state
+
+
 # Variable Name Pattern Matching Stuff
 
 DIRSC      = "DIRSC"                            # Directory Shortcut naming
@@ -626,6 +640,7 @@
 
 wBADCFGLINE = "Ignoring Line %s.\nBogus Configuration Entry:\n\n%s"
 wBADDEBUG   = "Ignoring Bogus Debug Level! - %s Is Not In Integer Or Hex Format."
+wBADENDIF   = "No Conditional Block To End!\nIgnoring Line %s:\n\n%s"
 wBADENVVBL  = "Ignoring Line %s.\nEnvironment Variable %s Not Set:\n\n%s"
 wBADEXE     = "Could Not Execute Command:\n\n%s"
 wBADRHS     = "Ignoring Line %s.\nOption Assignment Has Bad Righthand Side:\n\n%s"
@@ -696,7 +711,7 @@
 dOPTIONWIDTH = 16
 dSCWIDTH     = 6
 dTWOUPWIDTH  = 50
-dUSRVBLWIDTH = 16
+dUSRVBLWIDTH = 20
 
 # List of internal program variables to dump during debug sessions
 
@@ -815,14 +830,25 @@
 #####
 
 def ParseConfFile(event, DoOptionsProcessing=TRUE):
-    global CONF, UI
+    global CONF, UI, ConditionalStack
 
     # Cleanout any old configuration data
     UI.CmdTable  = {}
     UI.DirSCKeys = ["", "", "", "", "", "",
                    "", "", "", "", "", ""]
     UI.SymTable  = {}
-    linenum      = 0
+
+
+    # Initialize internal parsing data structures
+
+    linenum          = 0
+    ConditionalStack = [TRUE,]
+
+    # Load Symbol Table with predefined symbols
+
+    UI.SymTable[SYMOS] = os.name
+    UI.SymTable[SYMPLATFORM] = sys.platform
+
 
     # Unbind all existing key bindings
     for x in UI.KeyBindings.keys():
@@ -969,8 +995,14 @@
 
 
 def ParseLine(line, num):
-    global UI
+    global UI, ConditionalStack
+
+    ###
+    # Cleanup the line
+    ###
+    
     # Get rid of trailing newline, if any
+
     if line[-1] == '\n':
         line = line[:-1]
 
@@ -990,16 +1022,90 @@
     dummy.append("")
 
 
-    #####
+    # Before going on, make sure we're even supposed to process the line.
+    # If we are currently in the midst of a *false* conditional
+    # block, we must throw this line away.  The only thing
+    # we'll accept in that case is more conditional statements.
+
+    if (not ConditionalStack[-1]) and (dummy[0] not in (CONDIF, CONDENDIF)):
+        return
+    
+    ###
     # Blank Lines - Ignore
-    #####
+    ###
 
     if len(fields) == 0:
         pass
 
-    #####
-    # Variable Definitions
-    #####
+    ###
+    # Conditionals
+    ###
+
+    # Legal conditional statements are in one of several forms:
+    #
+    # .IF [SYMBOL]
+    # .IF [SYMBOL] == string
+    # .IF [SYMBOL]== string
+    # .IF [SYMBOL] ==string
+    # .IF [SYMBOL]==string
+    # .ENDIF
+
+    # Process conditional beginning-of-block statement
+
+    elif fields[0] == CONDIF:
+
+        # Process beginning of conditional block
+        if fields[0] == CONDIF:
+
+            # Process string equality checks
+            if line.count('=='):
+                pass
+
+            # Process variable existence checks
+            else:
+                # Existence checks must be in the form: .IF [VAR]
+                
+                if len(fields) != 2:
+                    WrnMsg(wBADCOND)
+                    return
+
+                # Presume 2nd field is in the form: [VAR]
+
+                if UI.SymTable.has_key(fields[1][1:-1]):
+                    conditional = TRUE
+                else:
+                    conditional = FALSE
+
+            # OK, now we save state of this conditional block
+            # If this is the first level of conditional, save it directly.
+
+            if len(ConditionalStack) == 1:
+                ConditionalStack.append(conditional)
+
+            # But, if we're nesting a conditional and the containing
+            # block is FALSE, so is the new block.
+
+            else:
+                ConditionalStack.append(ConditionalStack[-1] and conditional)
+
+    # Process conditional end-of-block statement
+    
+    elif fields[0] ==  CONDENDIF:
+
+        # The conditional stack must always have 1 value left in
+        # it after all conditional processing.  If it does not,
+        # it means there are more ENDIFs than IFs.
+        
+        if len(ConditionalStack) > 1:
+            ConditionalStack.pop()
+
+        else:
+            WrnMsg(wBADENDIF % (num,line))
+            
+    
+    ###
+    # Variable Definitions And Special Assignments
+    ###
 
     # A valid variable definition can
     # be 1, 2, or 3 fields:
@@ -1135,9 +1241,9 @@
         else:
             UI.SymTable[name] = val
 
-    #####
+    ###
     # Command Definitions
-    #####
+    ###
 
     elif len(fields[0]) == 1:
 
@@ -1440,9 +1546,9 @@
         # End of method 'twanderUI.__init__()'
 
 
-    #####
+    ###
     # Bind the relevant event handlers
-    #####
+    ###
         
     def BindAllHandlers(self):
 
@@ -1572,9 +1678,9 @@
         self.DirList.bind(self.KeyBindings["MOUSESEL"], MouseDblClick)
 
 
-        #####
+        ###
         # Directory Shortcut Keys - All Bound To A Common Handler
-        #####
+        ###
 
         self.DirList.bind(self.KeyBindings["KDIRSC1"],  lambda event :DirSCKeyPress(event, 1))
         self.DirList.bind(self.KeyBindings["KDIRSC2"],  lambda event :DirSCKeyPress(event, 2))
@@ -1621,9 +1727,9 @@
         self.DirList.bind(self.KeyBindings["MEMSET12"],  lambda event : KeyMemHandler(mem=12))
 
 
-        #####
+        ###
         # Sort Selection Keys - All Bound To A Common Handler
-        #####
+        ###
 
         self.DirList.bind(self.KeyBindings["SORTBY0"], lambda event : KeySetSortParm(parm=fNONE))
         self.DirList.bind(self.KeyBindings["SORTBY1"], lambda event : KeySetSortParm(parm=fPERMISSIONS))