Index: RollingFileAppender.cs
===================================================================
--- RollingFileAppender.cs	(revision 703602)
+++ RollingFileAppender.cs	(working copy)
@@ -452,7 +452,27 @@
 				}
 			}
 		}
-  
+
+        /// <summary>
+        /// Gets or sets a value indicating whether to preserve the file name extension when rolling.
+        /// </summary>
+        /// <value>
+        /// <c>true</c> if the file name extension should be preserved.
+        /// </value>
+        /// <remarks>
+        /// <para>
+        /// By default file.log is rolled to file.log.yyyy-mm-dd or file.log.curSizeRollBackup.
+        /// However, under Windows the new file name will loose any program associations as the
+        /// extension is changed. Optionally file.log can be renamed to file.yyyy-mm-dd.log or
+        /// file.curSizeRollBackup.log to maintain any program associations.
+        /// </para>
+        /// </remarks>
+        public bool PreserveLogFileNameExtension
+        {
+            get { return m_preserveLogFileNameExtension; }
+            set { m_preserveLogFileNameExtension = value; }
+        }
+
 		/// <summary>
 		/// Gets or sets a value indicating whether to always log to
 		/// the same file.
@@ -1046,6 +1066,19 @@
   
 		#region Roll File
 
+        private string CombinePath(string path1, string path2)
+        {
+            string extension = Path.GetExtension(path1);
+            if (m_preserveLogFileNameExtension && extension.Length > 0)
+            {
+                return Path.GetFileNameWithoutExtension(path1) + path2 + extension;
+            }
+            else
+            {
+                return path1 + path2;
+            }
+        }
+
 		/// <summary>
 		/// Rollover the file(s) to date/time tagged file(s).
 		/// </summary>
@@ -1072,9 +1105,9 @@
 				//something has gone wrong if we hit this -- we should only
 				//roll over if the new file will be different from the old
 				string dateFormat = m_now.ToString(m_datePattern, System.Globalization.DateTimeFormatInfo.InvariantInfo);
-				if (m_scheduledFilename.Equals(File + dateFormat)) 
+                if (m_scheduledFilename.Equals(CombinePath(File, dateFormat))) 
 				{
-					ErrorHandler.Error("Compare " + m_scheduledFilename + " : " + File + dateFormat);
+                    ErrorHandler.Error("Compare " + m_scheduledFilename + " : " + CombinePath(File, dateFormat));
 					return;
 				}
 	  
@@ -1087,8 +1120,8 @@
 				//we may have to roll over a large number of backups here
 				for (int i = 1; i <= m_curSizeRollBackups; i++) 
 				{
-					string from = File + '.' + i;
-					string to = m_scheduledFilename + '.' + i;
+                    string from = CombinePath(File, "." + i);
+                    string to = CombinePath(m_scheduledFilename, "." + i);
 					RollFile(from, to);
 				}
 	  
@@ -1099,7 +1132,7 @@
 			m_curSizeRollBackups = 0; 
 	
 			//new scheduled name
-			m_scheduledFilename = File + m_now.ToString(m_datePattern, System.Globalization.DateTimeFormatInfo.InvariantInfo);
+            m_scheduledFilename = CombinePath(File, m_now.ToString(m_datePattern, System.Globalization.DateTimeFormatInfo.InvariantInfo));
 
 			if (fileIsOpen)
 			{
@@ -1308,20 +1341,20 @@
 					// Delete the oldest file, to keep Windows happy.
 					if (m_curSizeRollBackups == m_maxSizeRollBackups) 
 					{
-						DeleteFile(baseFileName + '.' + m_maxSizeRollBackups);
+                        DeleteFile(CombinePath(baseFileName, "." + m_maxSizeRollBackups));
 						m_curSizeRollBackups--;
 					}
 	
 					// Map {(maxBackupIndex - 1), ..., 2, 1} to {maxBackupIndex, ..., 3, 2}
 					for (int i = m_curSizeRollBackups; i >= 1; i--) 
 					{
-						RollFile((baseFileName + "." + i), (baseFileName + '.' + (i + 1)));
+                        RollFile((CombinePath(baseFileName, "." + i)), (CombinePath(baseFileName, "." + (i + 1))));
 					}
 	
 					m_curSizeRollBackups++;
 
 					// Rename fileName to fileName.1
-					RollFile(baseFileName, baseFileName + ".1");
+                    RollFile(baseFileName, CombinePath(baseFileName, ".1"));
 				} 
 				else 
 				{
@@ -1351,13 +1384,13 @@
 						}
 
 						// Delete the archive file
-						DeleteFile(archiveFileBaseName + '.' + oldestFileIndex);
+                        DeleteFile(CombinePath(archiveFileBaseName, "." + oldestFileIndex));
 					}
 	
 					if (m_staticLogFileName) 
 					{
 						m_curSizeRollBackups++;
-						RollFile(baseFileName, baseFileName + '.' + m_curSizeRollBackups);
+                        RollFile(baseFileName, CombinePath(baseFileName, "." + m_curSizeRollBackups));
 					}
 				}
 			}
@@ -1528,6 +1561,12 @@
 		/// </summary>
 		private bool m_staticLogFileName = true;
   
+   		/// <summary>
+		/// Value indicating whether to preserve the file name extension when rolling.
+		/// </summary>
+		private bool m_preserveLogFileNameExtension = false;
+
+
 		/// <summary>
 		/// FileName provided in configuration.  Used for rolling properly
 		/// </summary>