patch 7.4.1575
Problem:    Using wrong size for struct.
Solution:   Use the size for wide API. (Ken Takata)
diff --git a/src/gui_w32.c b/src/gui_w32.c
index 6cc2e06..b2ee9ca 100644
--- a/src/gui_w32.c
+++ b/src/gui_w32.c
@@ -3682,10 +3682,9 @@
     filterp = convert_filterW(filter);
 
     vim_memset(&fileStruct, 0, sizeof(OPENFILENAMEW));
-#ifdef OPENFILENAME_SIZE_VERSION_400
+#ifdef OPENFILENAME_SIZE_VERSION_400W
     /* be compatible with Windows NT 4.0 */
-    /* TODO: what to use for OPENFILENAMEW??? */
-    fileStruct.lStructSize = OPENFILENAME_SIZE_VERSION_400;
+    fileStruct.lStructSize = OPENFILENAME_SIZE_VERSION_400W;
 #else
     fileStruct.lStructSize = sizeof(fileStruct);
 #endif