diff --git a/im/app/Makefile.in b/im/app/Makefile.in
index 32936302bd..7c2a7668fd 100644
--- a/im/app/Makefile.in
+++ b/im/app/Makefile.in
@@ -116,12 +116,6 @@ RCFLAGS += -DMOZ_INSTANTBIRD --include-dir $(srcdir)
 endif
 endif
 
-ifeq ($(OS_ARCH),OS2)
-RESFILE=splashos2.res
-RCFLAGS += -DMOZ_INSTANTBIRD
-RCFLAGS += -DINSTANTBIRD_ICO=\"$(DIST)/branding/instantbird.ico\"
-endif
-
 include $(topsrcdir)/config/rules.mk
 
 ifeq ($(OS_ARCH),WINNT)
@@ -147,12 +141,12 @@ endif
 endif
 endif
 
-ifneq (,$(filter-out OS2 WINNT,$(OS_ARCH)))
+ifneq ($(OS_ARCH),WINNT)
 libs::
 	cp -p $(MOZ_APP_NAME)$(BIN_SUFFIX) $(DIST)/bin/$(MOZ_APP_NAME)-bin$(BIN_SUFFIX)
 
 GARBAGE += $(addprefix $(DIST)/bin/defaults/pref/, all.js all-instantbird.js channel-prefs.js chat-prefs.js)
-endif # ! OS 2 or WinNT
+endif # ! WinNT
 
 endif # LIBXUL_SDK
 
diff --git a/im/content/preferences/preferences.xul b/im/content/preferences/preferences.xul
index 23b9235743..dc06f2f823 100644
--- a/im/content/preferences/preferences.xul
+++ b/im/content/preferences/preferences.xul
@@ -36,9 +36,6 @@
 #ifdef XP_WIN
 #define USE_WIN_TITLE_STYLE
 #endif
-#ifdef XP_OS2
-#define USE_WIN_TITLE_STYLE
-#endif
 
 <prefwindow type="prefwindow"
             id="BrowserPreferences"
diff --git a/im/installer/package-manifest.in b/im/installer/package-manifest.in
index 168d3de808..49bc2bfd55 100644
--- a/im/installer/package-manifest.in
+++ b/im/installer/package-manifest.in
@@ -634,14 +634,12 @@
 #ifdef XP_MACOSX
 @BINPATH@/crashreporter.app/
 #else
-#ifndef XP_OS2
 @BINPATH@/crashreporter@BIN_SUFFIX@
 @BINPATH@/crashreporter.ini
 #ifdef XP_UNIX
 @BINPATH@/Throbber-small.gif
 #endif
 #endif
-#endif
 #ifdef MOZ_CRASHREPORTER_INJECTOR
 @BINPATH@/breakpadinjector.dll
 #endif