diff --git a/Makefile.am b/Makefile.am
index 8b5d928f3..bec334354 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -723,7 +723,7 @@ EXTRA_DIST = \
   src/res/Play2.bmp \
   src/res/Brush2.bmp \
   src/res/oci.ico \
-  src/res/c4u.ico \
+  src/res/ocu.ico \
   src/res/Cursor.bmp \
   src/res/Grab.bmp \
   src/res/Line.bmp \
diff --git a/src/C4Application.cpp b/src/C4Application.cpp
index 77302010a..740c65d57 100644
--- a/src/C4Application.cpp
+++ b/src/C4Application.cpp
@@ -389,7 +389,7 @@ void C4Application::ParseCommandLine(int argc, char * argv[])
 			continue;
 		}
 		// Update file
-		if (SEqualNoCase(GetExtension(szParameter),"c4u"))
+		if (SEqualNoCase(GetExtension(szParameter),"ocu"))
 		{
 			Application.IncomingUpdate.Copy(szParameter);
 			continue;
diff --git a/src/c4group/C4Update.cpp b/src/c4group/C4Update.cpp
index 0709b5a62..1f4d202a7 100644
--- a/src/c4group/C4Update.cpp
+++ b/src/c4group/C4Update.cpp
@@ -115,7 +115,7 @@ bool C4Group_ApplyUpdate(C4Group &hGroup, unsigned long ParentProcessID)
 
 	// Process binary update group (AutoUpdate.txt found, additional binary files found)
 	if (hGroup.EntryCount(C4CFN_UpdateCore))
-		if (hGroup.EntryCount() - hGroup.EntryCount(C4CFN_UpdateCore) - hGroup.EntryCount("*.c4u") > 0)
+		if (hGroup.EntryCount() - hGroup.EntryCount(C4CFN_UpdateCore) - hGroup.EntryCount("*.ocu") > 0)
 		{
 			// Notice: AutoUpdate.txt is currently not processed...
 			char strEntry[_MAX_FNAME + 1] = "";
@@ -124,8 +124,8 @@ bool C4Group_ApplyUpdate(C4Group &hGroup, unsigned long ParentProcessID)
 			hGroup.ResetSearch();
 			// Look for binaries
 			while (hGroup.FindNextEntry("*", strEntry))
-				// Accept everything except *.c4u, AutoUpdate.txt, and c4group.exe (which is assumed not to work under Windows)
-				if (!WildcardMatch("*.c4u", strEntry) && !WildcardMatch(C4CFN_UpdateCore, strEntry) && !WildcardMatch("c4group.exe", strEntry))
+				// Accept everything except *.ocu, AutoUpdate.txt, and c4group.exe (which is assumed not to work under Windows)
+				if (!WildcardMatch("*.ocu", strEntry) && !WildcardMatch(C4CFN_UpdateCore, strEntry) && !WildcardMatch("c4group.exe", strEntry))
 					{ strList += strEntry; strList += ";"; }
 			// Extract binaries to current working directory
 			if (!hGroup.Extract(strList.getData()))
@@ -140,14 +140,14 @@ bool C4Group_ApplyUpdate(C4Group &hGroup, unsigned long ParentProcessID)
 				}
 		}
 
-	// Process any child updates (*.c4u)
-	if (hGroup.FindEntry("*.c4u"))
+	// Process any child updates (*.ocu)
+	if (hGroup.FindEntry("*.ocu"))
 	{
 		// Process all children
 		char strEntry[_MAX_FNAME + 1] = "";
 		C4Group hChild;
 		hGroup.ResetSearch();
-		while (hGroup.FindNextEntry("*.c4u", strEntry))
+		while (hGroup.FindNextEntry("*.ocu", strEntry))
 			if (hChild.OpenAsChild(&hGroup, strEntry))
 			{
 				bool ok = C4Group_ApplyUpdate(hChild, 0);
diff --git a/src/c4group/c4group_ng.cpp b/src/c4group/c4group_ng.cpp
index 74ff2e430..dfe0fbd56 100644
--- a/src/c4group/c4group_ng.cpp
+++ b/src/c4group/c4group_ng.cpp
@@ -518,7 +518,7 @@ int main(int argc, char *argv[])
 		printf("          -x:<command> Execute shell command when done\n");
 		printf("\n");
 		printf("Examples: c4group pack.ocg -x\n");
-		printf("          c4group update.c4u -g ver1.ocf ver2.ocf New_Version\n");
+		printf("          c4group update.ocu -g ver1.ocf ver2.ocf New_Version\n");
 		printf("          c4group -i\n");
 	}
 
diff --git a/src/gui/C4DownloadDlg.h b/src/gui/C4DownloadDlg.h
index 4fe49c379..aae05d801 100644
--- a/src/gui/C4DownloadDlg.h
+++ b/src/gui/C4DownloadDlg.h
@@ -16,7 +16,7 @@
  * See clonk_trademark_license.txt for full license.
  */
 // HTTP download dialog; downloads a file
-// (like, e.g., a .c4u update group)
+// (like, e.g., a .ocu update group)
 
 #ifndef INC_C4DownloadDlg
 #define INC_C4DownloadDlg
diff --git a/src/gui/C4UpdateDlg.cpp b/src/gui/C4UpdateDlg.cpp
index 959caae6b..4827c2c39 100644
--- a/src/gui/C4UpdateDlg.cpp
+++ b/src/gui/C4UpdateDlg.cpp
@@ -220,7 +220,7 @@ bool C4UpdateDlg::ApplyUpdate(const char *strUpdateFile, bool fDeleteUpdate, C4G
 		// ASK: What is this? Why should an update program not be found at the top
 		// level? This seems obsolete. - Newton
 		// Not found: look for an engine update pack one level down
-		if (UpdateGroup.FindEntry(FormatString("cr_*_%s.c4u", C4_OS).getData(), strSubGroup))
+		if (UpdateGroup.FindEntry(FormatString("cr_*_%s.ocu", C4_OS).getData(), strSubGroup))
 			// Extract update program from sub group
 			if (SubGroup.OpenAsChild(&UpdateGroup, strSubGroup))
 			{
diff --git a/src/platform/C4FileClasses.cpp b/src/platform/C4FileClasses.cpp
index d383f8d3c..4fd05c8c8 100644
--- a/src/platform/C4FileClasses.cpp
+++ b/src/platform/C4FileClasses.cpp
@@ -58,14 +58,14 @@ bool SetC4FileClasses(const char *szEnginePath)
 	if (!SetRegFileClass("OpenClonk.Binary",     ,"ocb", "OpenClonk Binary",            szEnginePath, 8, "application/octet-stream")) return false;
 	if (!SetRegFileClass("OpenClonk.Video",      ,"ocv", "OpenClonk Video",             szEnginePath, 9, "video/avi")) return false;
 	if (!SetRegFileClass("OpenClonk.Weblink",    ,"ocl", "OpenClonk Weblink",           szEnginePath, 10, C4FileClassContentType)) return false;
-	if (!SetRegFileClass("Clonk4.Update",     "c4u", "Clonk 4 Update",            szEnginePath, 11, C4FileClassContentType)) return false;
+	if (!SetRegFileClass("OpenClonk.Update",     ,"ocu", "OpenClonk Update",            szEnginePath, 11, C4FileClassContentType)) return false;
 
 	if (!SetProtocol("clonk", "%s %%1 /Fullscreen", szEnginePath)) return false;
 
 	char strCommand[2048];
-	// c4u application: send to engine
+	// ocu application: send to engine
 	sprintf(strCommand, "\"%s\" \"%%1\"", szEnginePath);
-	if (!SetRegShell("Clonk4.Update", "Update", "Update", strCommand, true)) return false;
+	if (!SetRegShell("OpenClonk.Update", "Update", "Update", strCommand, true)) return false;
 
 	// kill old App Paths registration
 	DeleteRegistryKey(HKEY_LOCAL_MACHINE, "Software\\Microsoft\\Windows\\CurrentVersion\\App Paths\\Clonk.exe");
diff --git a/src/res/c4u.ico b/src/res/c4u.ico
deleted file mode 100644
index cff325359..000000000
Binary files a/src/res/c4u.ico and /dev/null differ
diff --git a/src/res/engine.rc b/src/res/engine.rc
index 074db1567..ff62ad72d 100644
--- a/src/res/engine.rc
+++ b/src/res/engine.rc
@@ -42,7 +42,7 @@ IDI_08_OCM              ICON    DISCARDABLE     "ocm.ico"
 IDI_09_OCB              ICON    DISCARDABLE     "ocb.ico"
 IDI_10_OCV              ICON    DISCARDABLE     "ocv.ico"
 IDI_11_OCL              ICON    DISCARDABLE     "ocl.ico"
-IDI_13_C4U              ICON    DISCARDABLE     "c4u.ico"
+IDI_13_OCU              ICON    DISCARDABLE     "ocu.ico"
 
 #ifdef APSTUDIO_INVOKED
 /////////////////////////////////////////////////////////////////////////////
diff --git a/src/res/ocu.ico b/src/res/ocu.ico
new file mode 100644
index 000000000..714ecb48f
Binary files /dev/null and b/src/res/ocu.ico differ
diff --git a/src/res/resource.h b/src/res/resource.h
index c7a0445c8..0e7df237b 100644
--- a/src/res/resource.h
+++ b/src/res/resource.h
@@ -69,7 +69,7 @@
 #define IDI_09_OCB                      4009
 #define IDI_10_OCV                      4010
 #define IDI_11_OCL                      4011
-#define IDI_13_C4U                      4013
+#define IDI_13_OCU                      4013
 #define IDM_FILE_CLOSE                  5003
 #define IDM_FILE_OPEN                   5004
 #define IDM_FILE_OPENWPLRS              5005
diff --git a/tools/install/oc.nsi b/tools/install/oc.nsi
index b1e412988..193c7bd58 100644
--- a/tools/install/oc.nsi
+++ b/tools/install/oc.nsi
@@ -123,8 +123,8 @@ Section -Post
   WriteRegStr HKCR ".ocv\Content Type" "" "video/avi"
   WriteRegStr HKCR ".ocl" "" "OpenClonk.Weblink"
   WriteRegStr HKCR ".ocl\Content Type" "" "vnd.clonk.c4group"
-  WriteRegStr HKCR ".c4u" "" "Clonk4.Update"
-  WriteRegStr HKCR ".c4u\Content Type" "" "vnd.clonk.c4group"
+  WriteRegStr HKCR ".ocu" "" "OpenClonk.Update"
+  WriteRegStr HKCR ".ocu\Content Type" "" "vnd.clonk.c4group"
 ; Register file classes  
   WriteRegStr HKCR "OpenClonk.Scenario" "" "OpenClonk Scenario"
   WriteRegStr HKCR "OpenClonk.Scenario\DefaultIcon" "" "$INSTDIR\Clonk.exe,1"
@@ -146,11 +146,11 @@ Section -Post
   WriteRegStr HKCR "OpenClonk.Video\DefaultIcon" "" "$INSTDIR\Clonk.exe,9"
   WriteRegStr HKCR "OpenClonk.Weblink" "" "OpenClonk Weblink"
   WriteRegStr HKCR "OpenClonk.Weblink\DefaultIcon" "" "$INSTDIR\Clonk.exe,10"
-  WriteRegStr HKCR "Clonk4.Update" "" "Clonk 4 Update"
-  WriteRegStr HKCR "Clonk4.Update\DefaultIcon" "" "$INSTDIR\Clonk.exe,11"
+  WriteRegStr HKCR "OpenClonk.Update" "" "OpenClonk Update"
+  WriteRegStr HKCR "OpenClonk.Update\DefaultIcon" "" "$INSTDIR\Clonk.exe,11"
 ; Register additional file handling
-  WriteRegStr HKCR "Clonk4.Update\Shell\Update" "" "Update"
-  WriteRegStr HKCR "Clonk4.Update\Shell\Update\Command" "" "$\"$INSTDIR\Clonk.exe$\" $\"%1$\""
+  WriteRegStr HKCR "OpenClonk.Update\Shell\Update" "" "Update"
+  WriteRegStr HKCR "OpenClonk.Update\Shell\Update\Command" "" "$\"$INSTDIR\Clonk.exe$\" $\"%1$\""
 ; Remove old use of App Paths   
   DeleteRegKey HKLM "Software\Microsoft\Windows\CurrentVersion\App Paths\Clonk.exe"    
 SectionEnd
@@ -215,8 +215,8 @@ Section Uninstall
   DeleteRegKey HKCR "OpenClonk.Video"
   DeleteRegKey HKCR ".ocl"
   DeleteRegKey HKCR "OpenClonk.Weblink"
-  DeleteRegKey HKCR ".c4u"
-  DeleteRegKey HKCR "Clonk4.Update"
+  DeleteRegKey HKCR ".ocu"
+  DeleteRegKey HKCR "OpenClonk.Update"
   
   ; Start menu shortcuts (All Users)
   SetShellVarContext all