edit: $/Dev10/feature/vs_langs01/Merlin/Main/Languages/Ruby/context.rb;C521915
File: context.rb
===================================================================
--- $/Dev10/feature/vs_langs01/Merlin/Main/Languages/Ruby/context.rb;C521915  (server)    8/6/2008 2:43 PM
+++ Shelved Change: $/Dev10/feature/vs_langs01/Merlin/Main/Languages/Ruby/context.rb;unniseo
@@ -775,13 +775,13 @@
   def self.find_executable(executable)
     executable.downcase!
     result = []
-    search_path = ENV['PATH'].split(';')
+    search_path = ENV['PATH'].split(File::PATH_SEPARATOR)
     search_path.each do |dir|
-      path = dir.gsub '\\', '/'
-      Dir[path + '/*.exe'].each do |file|
-        file_path = Pathname.new(file)
-        result << file_path.dirname if file_path.basename.downcase == executable
-      end
+      path = Pathname.new(dir)
+      file_path = path + executable
+      result << file_path.dirname if file_path.exist?
+      file_path = path + executable + '.exe'
+      result << file_path.dirname if file_path.exist?
     end
     result
   end
@@ -806,11 +806,11 @@
     load path_to_config if File.exist? path_to_config
 
     unless defined?(UserEnvironment::MRI)
-      ruby_exe_paths = UserEnvironment.find_executable 'ruby.exe'
-      if ruby_exe_paths.length == 1
+      ruby_exe_paths = UserEnvironment.find_executable 'ruby'
+      unless ruby_exe_paths.empty?
         UserEnvironment.const_set(:MRI, Pathname.new(ruby_exe_paths.first + '\..\\'))
       else
-        raise ArgumentError.new("Found more than one version of ruby.exe on your path #{ruby_exe_paths.join(', ')}")
+        raise ArgumentError.new("Could not find ruby.exe on your path")
       end
     end
     UserEnvironment.const_set(:TAGS, "#{ENV['HOME']}\\dev\\ironruby-tags".gsub('\\', '/')) unless defined?(UserEnvironment::TAGS)
===================================================================
edit: $/Dev10/feature/vs_langs01/Merlin/Main/Languages/Ruby/Rakefile;C521915
edit: $/Dev10/feature/vs_langs01/Merlin/Main/Languages/Ruby/Libraries.LCA_RESTRICTED/Builtins/FileOps.cs;C521915
File: FileOps.cs
===================================================================
--- $/Dev10/feature/vs_langs01/Merlin/Main/Languages/Ruby/Libraries.LCA_RESTRICTED/Builtins/FileOps.cs;C521915  (server)    8/7/2008 9:11 AM
+++ Shelved Change: $/Dev10/feature/vs_langs01/Merlin/Main/Languages/Ruby/Libraries.LCA_RESTRICTED/Builtins/FileOps.cs;unniseo
@@ -219,10 +219,54 @@
 
         [RubyMethod("dirname", RubyMethodAttributes.PublicSingleton)]
         public static MutableString/*!*/ DirName(CodeContext/*!*/ context, object/*!*/ self, MutableString/*!*/ path) {
-            string directoryName = System.IO.Path.GetDirectoryName(path.ConvertToString());
+            string directoryName = path.ConvertToString();
+            if (IsValidPath(path.ConvertToString()))
+            {
+                directoryName = System.IO.Path.GetDirectoryName(path.ConvertToString());
+                string fileName = System.IO.Path.GetFileName(path.ConvertToString());
+                if (!String.IsNullOrEmpty(fileName))
+                {
+                    directoryName = StripPathCharacters(path.ConvertToString().Replace(fileName, ""));
+                }
+            }
+            else
+            {
+                if (directoryName.Length > 1)
+                    directoryName = "//";
+            }
             return Glob.CanonicalizePath(MutableString.Create(String.IsNullOrEmpty(directoryName) ? "." : directoryName));
         }
 
+         private static bool IsValidPath(string path)
+        {
+            int length = 0;
+            foreach (char c in path.ToCharArray())
+            {
+                if ((c == '/') || (c == '\\'))
+                    continue;
+                length++;
+            }
+            return (length > 0);
+
+        }
+
+        private static string StripPathCharacters(string path)
+        {
+            int limit=0;
+            for (int charIndex = path.Length - 1; charIndex > 0; charIndex--)
+            {
+                if (!((path[charIndex] == '/') || (path[charIndex] == '\\')))
+                    break;
+                limit++;
+            }
+            if (limit > 0)
+            {
+                limit--;
+                return path.Substring(0, path.Length - limit - 1);
+            }
+            return path;
+        }
+
         [RubyMethod("executable?", RubyMethodAttributes.PublicSingleton)]
         [RubyMethod("executable_real?", RubyMethodAttributes.PublicSingleton)]
         public static bool IsExecutable(CodeContext/*!*/ context, object self, [NotNull]MutableString/*!*/ path) {
@@ -767,6 +811,7 @@
 
         private readonly static MutableString INTERNAL_SEPARATOR = MutableString.Create("/");
 
+        private readonly static string NUL_VALUE = "NUL";
         [RubyConstant]
         public readonly static MutableString SEPARATOR = INTERNAL_SEPARATOR;
 
@@ -843,6 +888,8 @@
                     result = new FileInfo(path);                    
                 } else if (pal.DirectoryExists(path)) {
                     result = new DirectoryInfo(path);                    
+                } else if (path.ToUpper().Equals(NUL_VALUE)) {
+                    result = null;
                 } else {
                     return false;
                 }
===================================================================