diff --git a/pkg/replacefile/doc.go b/pkg/replacefile/doc.go
new file mode 100644
index 0000000..acf1839
--- /dev/null
+++ b/pkg/replacefile/doc.go
@@ -0,0 +1,6 @@
+// Copyright (c) 2012 The Grumble Authors
+// The use of this source code is goverened by a BSD-style
+// license that can be found in the LICENSE-file.
+
+// Package replacefile implements access to the ReplaceFile Win32 API.
+package replacefile
\ No newline at end of file
diff --git a/pkg/replacefile/flags.go b/pkg/replacefile/flags.go
new file mode 100644
index 0000000..9ab9542
--- /dev/null
+++ b/pkg/replacefile/flags.go
@@ -0,0 +1,12 @@
+// Copyright (c) 2012 The Grumble Authors
+// The use of this source code is goverened by a BSD-style
+// license that can be found in the LICENSE-file.
+
+package replacefile
+
+type Flag uint32
+
+const (
+	IgnoreMergeErrors Flag = 0x2
+	IgnoreACLErrors   Flag = 0x4
+)
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diff --git a/pkg/replacefile/replacefile_stub.go b/pkg/replacefile/replacefile_stub.go
new file mode 100644
index 0000000..da0b9e3
--- /dev/null
+++ b/pkg/replacefile/replacefile_stub.go
@@ -0,0 +1,22 @@
+// Copyright (c) 2012 The Grumble Authors
+// The use of this source code is goverened by a BSD-style
+// license that can be found in the LICENSE-file.
+
+// +build !windows
+
+package replacefile
+
+import (
+	"errors"
+)
+
+var (
+	errOnlyWindows = errors.New("replacefile: only implemented on Windows")
+	ErrUnableToMoveReplacement error = errOnlyWindows
+	ErrUnableToMoveReplacement2 error = errOnlyOnWindows
+	ErrUnableToRemoveReplaced error = errOnlyWindows
+)
+
+func ReplaceFile(replaced string, replacement string, backup string, flags Flag) error {
+	return errOnlyWindows
+}
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diff --git a/pkg/replacefile/replacefile_windows.go b/pkg/replacefile/replacefile_windows.go
new file mode 100644
index 0000000..c46523d
--- /dev/null
+++ b/pkg/replacefile/replacefile_windows.go
@@ -0,0 +1,62 @@
+// Copyright (c) 2012 The Grumble Authors
+// The use of this source code is goverened by a BSD-style
+// license that can be found in the LICENSE-file.
+
+package replacefile
+
+import (
+	"unsafe"
+	"syscall"
+)
+
+var (
+	modkernel32       = syscall.NewLazyDLL("kernel32.dll")
+	procReplaceFileW  = modkernel32.NewProc("ReplaceFileW")
+)
+
+// Define the syscall.Errno backed-errors here in order to get a cleaner
+// godoc output.
+var (
+	win32_ERROR_UNABLE_TO_MOVE_REPLACEMENT = syscall.Errno(0x498)
+	win32_ERROR_UNABLE_TO_MOVE_REPLACEMENT_2 = syscall.Errno(0x499)
+	win32_ERROR_UNABLE_TO_REMOVE_REPLACED = syscall.Errno(0x497)
+)
+
+var (
+	ErrUnableToMoveReplacement error = win32_ERROR_UNABLE_TO_MOVE_REPLACEMENT
+	ErrUnableToMoveReplacement2 error = win32_ERROR_UNABLE_TO_MOVE_REPLACEMENT_2
+	ErrUnableToRemoveReplaced error = win32_ERROR_UNABLE_TO_REMOVE_REPLACED
+)
+
+func replaceFileW(replaced *uint16, replacement *uint16, backup *uint16, flags uint32) (err error) {
+	r1, _, e1 := syscall.Syscall6(procReplaceFileW.Addr(), 6, uintptr(unsafe.Pointer(replaced)), uintptr(unsafe.Pointer(replacement)), uintptr(unsafe.Pointer(backup)), uintptr(flags), 0, 0)
+	if r1 == 0 {
+		if e1 != 0 {
+			err = error(e1)
+		} else {
+			err = syscall.EINVAL
+		}
+	}
+	return
+}
+
+// ReplaceFile calls through to the Win32 ReplaceFile API, which can be found at the following
+// URL: http://msdn.microsoft.com/en-us/library/windows/desktop/aa365512(v=vs.85).aspx
+func ReplaceFile(replaced string, replacement string, backup string, flags Flag) error {
+	replacedPtr, err := syscall.UTF16PtrFromString(replaced)
+	if err != nil {
+		return err
+	}
+
+	replacementPtr, err := syscall.UTF16PtrFromString(replacement)
+	if err != nil {
+		return err
+	}
+
+	backupPtr, err := syscall.UTF16PtrFromString(backup)
+	if err != nil {
+		return err
+	}
+
+	return replaceFileW(replacedPtr, replacementPtr, backupPtr, uint32(flags))
+}
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