diff --git a/build/jam/BuildSetup b/build/jam/BuildSetup
index b4939b58c6..939bf12976 100644
--- a/build/jam/BuildSetup
+++ b/build/jam/BuildSetup
@@ -242,23 +242,17 @@ HOST_UNARFLAGS		?= x ;
 
 # check the host platform compatibility
 SetPlatformCompatibilityFlagVariables HOST_PLATFORM : HOST : host
-	: linux openbsd freebsd darwin sunos cygwin ;
+	: linux openbsd freebsd darwin ;
 HOST_PLATFORM_(host)_COMPATIBLE = 1 ;
 
 if $(HOST_PLATFORM) = linux || $(HOST_PLATFORM) = freebsd
-	|| $(HOST_PLATFORM) = darwin || $(HOST_PLATFORM) = cygwin
-	|| $(HOST_PLATFORM) = sunos || $(HOST_PLATFORM) = openbsd {
+	|| $(HOST_PLATFORM) = darwin || $(HOST_PLATFORM) = openbsd {
 	# don't use lex: otherwise rc will not work correctly
 	if $(LEX) = lex {
 		LEX = flex ;
 	}
 }
 
-if $(HOST_PLATFORM) = cygwin {
-	HOST_LINKFLAGS += -Xlinker --allow-multiple-definition -Xlinker
-		--enable-auto-import ;
-}
-
 HOST_CPU ?= $(OSPLAT:L) ;
 
 # Jam doesn't know x86_64, so override HOST_CPU, if 64 bit.
@@ -304,10 +298,8 @@ HOST_ASFLAGS = ;
 HOST_CCFLAGS += -Wno-multichar ;
 HOST_C++FLAGS += -Wno-multichar ;
 
-if $(HOST_PLATFORM) != cygwin {
-	HOST_PIC_CCFLAGS += -fPIC ;
-	HOST_PIC_C++FLAGS += -fPIC ;
-}
+HOST_PIC_CCFLAGS += -fPIC ;
+HOST_PIC_C++FLAGS += -fPIC ;
 
 if $(HOST_GCC_VERSION[1]) >= 3 {
 	HOST_GCC_BASE_FLAGS += -fno-strict-aliasing -fno-delete-null-pointer-checks ;
@@ -433,7 +425,7 @@ if $(HOST_PLATFORM_BEOS_COMPATIBLE) {
 } else {
 	HOST_LINKFLAGS += -lm -ldl ;
 	HOST_LIBSTDC++ = stdc++ ;
-	if $(HOST_PLATFORM) = cygwin {
+	if $(HOST_PLATFORM) = mingw {
 		HOST_ADD_BUILD_COMPATIBILITY_LIB_DIR
 			= "export PATH=$PATH:$(HOST_BUILD_COMPATIBILITY_LIB_DIR)" ;
 	} else if $(HOST_PLATFORM) = darwin {
@@ -444,14 +436,7 @@ if $(HOST_PLATFORM_BEOS_COMPATIBLE) {
 			= "export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$(HOST_BUILD_COMPATIBILITY_LIB_DIR)" ;
 	}
 
-	if $(HOST_PLATFORM) = cygwin {
-		# not needed
-		HOST_PTHREAD_LINKFLAGS = ;
-	} else if $(HOST_PLATFORM) = freebsd {
-		HOST_PTHREAD_LINKFLAGS = -pthread ;
-	} else {
-		HOST_PTHREAD_LINKFLAGS = -pthread ;
-	}
+	HOST_PTHREAD_LINKFLAGS = -pthread ;
 
 	# the C++ support library
 	if $(HOST_GCC_VERSION[1]) < 3 {
@@ -685,8 +670,6 @@ switch $(HOST_PLATFORM) {
 	case linux		: HOST_DEFINES	+= HAIKU_HOST_PLATFORM_LINUX ;
 	case freebsd	: HOST_DEFINES	+= HAIKU_HOST_PLATFORM_FREEBSD ;
 	case darwin		: HOST_DEFINES	+= HAIKU_HOST_PLATFORM_DARWIN ;
-	case cygwin		: HOST_DEFINES	+= HAIKU_HOST_PLATFORM_CYGWIN ;
-	case sunos		: HOST_DEFINES	+= HAIKU_HOST_PLATFORM_SUNOS ;
 }
 
 # define host platform 64 bit macro
diff --git a/build/jam/MainBuildRules b/build/jam/MainBuildRules
index b85b2d3398..5652f4503f 100644
--- a/build/jam/MainBuildRules
+++ b/build/jam/MainBuildRules
@@ -621,7 +621,7 @@ rule BuildPlatformObjects
 	Objects $(sources) ;
 }
 
-actions CygwinExtensionFix
+actions Win32ExtensionFix
 {
 	if test -f $(1).exe ; then
 		rm -f $(1)
@@ -658,14 +658,14 @@ rule BuildPlatformMain
 
 	Main $(target) : $(sources) ;
 	LinkAgainst $(target) : $(libs) ;
-	if $(HOST_PLATFORM) = cygwin {
-		# Cygwin gcc adds the ".exe" extension. We cannot force
+	if $(HOST_PLATFORM) = mingw {
+		# MinGW GCC adds the ".exe" extension. We cannot force
 		# jam to use SUFEXE as haiku target executables are not
 		# supposed to have this extension, thus finding
 		# dependencies will fail for these.
 		# The hack is to remove the extension after a successful
 		# build of the Target.
-		CygwinExtensionFix $(target) ;
+		Win32ExtensionFix $(target) ;
 	}
 }
 
@@ -685,9 +685,9 @@ rule BuildPlatformSharedLibrary
 	if $(HOST_PLATFORM) = darwin {
 		LINKFLAGS on $(target) = [ on $(target) return $(LINKFLAGS) ]
 			-dynamic -dynamiclib -Xlinker -flat_namespace ;
-	} else if $(HOST_PLATFORM) = cygwin {
-		LINKFLAGS on $(target) = [ on $(target) return $(LINKFLAGS) ]
-			-shared -Xlinker --allow-multiple-definition ;
+#	} else if $(HOST_PLATFORM) = cygwin {
+#		LINKFLAGS on $(target) = [ on $(target) return $(LINKFLAGS) ]
+#			-shared -Xlinker --allow-multiple-definition ;
 	} else {
 		LINKFLAGS on $(target) = [ on $(target) return $(LINKFLAGS) ]
 			-shared -Xlinker -soname=\"$(target:G=)\" ;
diff --git a/configure b/configure
index 701684a800..f21bc513bf 100755
--- a/configure
+++ b/configure
@@ -782,8 +782,6 @@ case "${platform}" in
 	Haiku)	HOST_PLATFORM=haiku_host ;;
 	Linux)	HOST_PLATFORM=linux ;;
 	OpenBSD) HOST_PLATFORM=openbsd ;;
-	SunOS)	HOST_PLATFORM=sunos ;;
-	CYGWIN_NT-*) HOST_PLATFORM=cygwin ;;
 	*)		echo Unsupported platform: ${platform}
 			exit 1 ;;
 esac
diff --git a/headers/build/BeOSBuildCompatibility.h b/headers/build/BeOSBuildCompatibility.h
index 582f97e1cb..fdc909d8e5 100644
--- a/headers/build/BeOSBuildCompatibility.h
+++ b/headers/build/BeOSBuildCompatibility.h
@@ -1,20 +1,12 @@
 #ifndef BEOS_BUILD_COMPATIBILITY_H
 #define BEOS_BUILD_COMPATIBILITY_H
 
-#if defined(HAIKU_HOST_PLATFORM_CYGWIN)
-#	ifndef __addr_t_defined
-#		define __addr_t_defined
-#	endif
-#endif
-
-// DEFFILEMODE is not available on Cygwin, SunOS and when building with musl c
-#if defined(HAIKU_HOST_PLATFORM_CYGWIN) || defined(HAIKU_HOST_PLATFORM_SUNOS) \
-	|| !defined(DEFFILEMODE)
+// DEFFILEMODE is not available on MinGW and on platforms with MUSL
 #ifndef DEFFILEMODE
 #define DEFFILEMODE (S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH)
 #endif
 
-// There's no ALLPERMS when building with musl c
+// There's no ALLPERMS on platforms with MUSL
 #ifndef ALLPERMS
 #	define ALLPERMS (S_ISUID|S_ISGID|S_ISVTX|S_IRWXU|S_IRWXG|S_IRWXO)
 #endif
@@ -23,16 +15,6 @@
 #define	S_IUMSK 07777
 #endif
 
-#include <ctype.h>
-#endif
-
-#ifdef HAIKU_HOST_PLATFORM_SUNOS
-#	include <limits.h>
-#	ifndef NAME_MAX
-#		define NAME_MAX	MAXNAMELEN
-#	endif
-#endif
-
 typedef unsigned long	haiku_build_addr_t;
 #define addr_t			haiku_build_addr_t
 
@@ -62,7 +44,7 @@ extern size_t	strlcat(char* dest, const char* source, size_t length);
 extern size_t	strnlen(const char* string, size_t length);
 #endif
 
-#if defined(HAIKU_HOST_PLATFORM_CYGWIN) || defined(HAIKU_HOST_PLATFORM_SUNOS)
+#if defined(HAIKU_HOST_PLATFORM_MINGW)
 extern char*	stpcpy(char* dest, const char* src);
 extern char*	strcasestr(const char* s, const char* find);
 #endif
diff --git a/src/build/libroot/Jamfile b/src/build/libroot/Jamfile
index 1d22d3cd33..779126bad0 100644
--- a/src/build/libroot/Jamfile
+++ b/src/build/libroot/Jamfile
@@ -40,7 +40,7 @@ if $(HOST_PLATFORM) != darwin && $(HOST_PLATFORM) != haiku_host {
 	strlSources = strlcpy.c strlcat.c ;
 }
 
-if $(HOST_PLATFORM) = cygwin || $(HOST_PLATFORM) = sunos {
+if $(HOST_PLATFORM) = mingw {
 	strlSources += stpcpy.c strcasestr.c ;
 }
 
diff --git a/src/tools/makebootable/platform/bios_ia32/Jamfile b/src/tools/makebootable/platform/bios_ia32/Jamfile
index f64aeaad0e..68045206f1 100644
--- a/src/tools/makebootable/platform/bios_ia32/Jamfile
+++ b/src/tools/makebootable/platform/bios_ia32/Jamfile
@@ -27,8 +27,7 @@ if $(HOST_PLATFORM) = linux || $(HOST_PLATFORM) = freebsd || $(HOST_PLATFORM) =
 
 # Write the stage 1 boot loader into the makebootable resources. On Darwin
 # resources don't seem to work; there we use an attribute instead.
-if $(HOST_PLATFORM) != darwin && $(HOST_PLATFORM) != cygwin
-	&& $(HOST_PLATFORM) != sunos {
+if $(HOST_PLATFORM) != darwin && $(HOST_PLATFORM) != mingw {
 	AddFileDataResource <build>makebootable : RAWT:666:BootCode : stage1.bin ;
 }
 
@@ -39,7 +38,6 @@ BuildPlatformMain <build>makebootable :
 ;
 
 # on Darwin write the boot loader code into an attribute
-if $(HOST_PLATFORM) = darwin || $(HOST_PLATFORM) = cygwin
-	|| $(HOST_PLATFORM) = sunos {
+if $(HOST_PLATFORM) = darwin || $(HOST_PLATFORM) = mingw {
 	AddFileDataAttribute <build>makebootable : BootCode : raw : stage1.bin ;
 }