Index: src/org/jruby/ext/posix/WindowsLibC.java
===================================================================
--- src/org/jruby/ext/posix/WindowsLibC.java	(revision 79b6c76b222f0e9b06f4b8d8d02f59006a483602)
+++ src/org/jruby/ext/posix/WindowsLibC.java	(revision )
@@ -1,14 +1,39 @@
 package org.jruby.ext.posix;
 
+import com.kenai.jaffl.Pointer;
 import com.kenai.jaffl.annotations.In;
 import com.kenai.jaffl.annotations.StdCall;
 
 public interface WindowsLibC extends LibC {
     public int _open_osfhandle(int handle, int flags);
-    public int _utime64(String filename, UTimBuf64 times);
+
     public int _wmkdir(@In byte[] path);
+
     @StdCall
     public int GetFileType(int handle);
+
     @StdCall
-    public boolean CreateHardLinkA(String oldname, String newName, @In byte[] reserved);
+    public boolean CreateHardLinkW(byte[] oldname, byte[] newName, @In byte[] reserved);
+
+    @StdCall
+    int CreateFileW(
+            byte[] lpFileName,
+            int dwDesiredAccess,
+            int dwShareMode,
+            Pointer lpSecurityAttributes,
+            int dwCreationDisposition,
+            int dwFlagsAndAttributes,
+            int hTemplateFile
+    );
+
+    @StdCall
+    boolean SetFileTime(
+            int hFile,
+            FileTime lpCreationTime,
+            FileTime lpLastAccessTime,
+            FileTime lpLastWriteTime
+    );
+
+    @StdCall
+    boolean CloseHandle(int handle);
 }
Index: src/org/jruby/ext/posix/FileTime.java
===================================================================
--- src/org/jruby/ext/posix/FileTime.java	(revision )
+++ src/org/jruby/ext/posix/FileTime.java	(revision )
@@ -0,0 +1,8 @@
+package org.jruby.ext.posix;
+
+import com.kenai.jaffl.struct.Struct;
+
+public class FileTime extends Struct {
+  public final Unsigned32 dwLowDateTime = new Unsigned32();
+  public final Unsigned32 dwHighDateTime = new Unsigned32();
+}
Index: test/org/jruby/ext/posix/FileTest.java
===================================================================
--- test/org/jruby/ext/posix/FileTest.java	(revision )
+++ test/org/jruby/ext/posix/FileTest.java	(revision )
@@ -0,0 +1,59 @@
+package org.jruby.ext.posix;
+
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.io.File;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public class FileTest {
+    private static POSIX posix;
+
+    @BeforeClass
+    public static void setUpClass() throws Exception {
+        posix = POSIXFactory.getPOSIX(new DummyPOSIXHandler(), true);
+    }
+
+    @Test
+    public void utimeTest() throws Throwable {
+        File f = File.createTempFile("utime", null);
+        long oldTime = posix.stat(f.getAbsolutePath()).mtime();
+        Thread.sleep(2000);
+        int rval = posix.utimes(f.getAbsolutePath(), null, null);
+        assertEquals("utime did not return 0", 0, rval);
+        long newTime = posix.stat(f.getAbsolutePath()).mtime();
+        f.delete();
+        assertTrue("mtime failed", newTime > oldTime);
+    }
+
+    @Test
+    public void linkTest() throws Throwable {
+        File f1 = File.createTempFile("utime", null);
+        File f2 = new File(f1.getAbsolutePath() + "link");
+        int rval = posix.link(f1.getAbsolutePath(), f2.getAbsolutePath());
+        assertEquals("link did not return 0", 0, rval);
+        assertTrue("Link was not created", f2.exists());
+        f1.delete();
+        f2.delete();
+    }
+
+    @Test
+    public void mkdirRelativeTest() throws Throwable {
+        File dir = new File("tmp");
+        int rval = posix.mkdir(dir.getPath(), 0);
+        assertEquals("mkdir did not return 0", 0, rval);
+        assertTrue("Directory was not created", dir.exists());
+        dir.delete();
+    }
+
+    @Test
+    public void mkdirAbsoluteTest() throws Throwable {
+        File dir = new File("tmp");
+        int rval = posix.mkdir(dir.getAbsolutePath(), 0);
+        assertEquals("mkdir did not return 0", 0, rval);
+        assertTrue("Directory was not created", dir.exists());
+        dir.delete();
+    }
+}
Index: src/org/jruby/ext/posix/WindowsPOSIX.java
===================================================================
--- src/org/jruby/ext/posix/WindowsPOSIX.java	(revision 79b6c76b222f0e9b06f4b8d8d02f59006a483602)
+++ src/org/jruby/ext/posix/WindowsPOSIX.java	(revision )
@@ -4,12 +4,15 @@
 import static com.kenai.constantine.platform.Errno.*;
 import static com.kenai.constantine.platform.windows.LastError.*;
 
+import java.io.File;
 import java.io.FileDescriptor;
-import java.io.UnsupportedEncodingException;
+import java.nio.charset.Charset;
 import java.util.HashMap;
 import java.util.Map;
 
 final class WindowsPOSIX extends BaseNativePOSIX {
+    private static final Charset UTF16_LE = Charset.forName("UTF-16LE");
+
     private final static int FILE_TYPE_CHAR = 0x0002;
 
     private final static Map<Integer, Errno> errorToErrnoMapper
@@ -250,15 +253,81 @@
         return null;
     }
 
+    private static final int INVALID_HANDLE_VALUE = -1;
+
+    private static final int GENERIC_ALL = 0x10000000;
+    private static final int GENERIC_READ = 0x80000000;
+    private static final int GENERIC_WRITE = 0x40000000;
+    private static final int GENERIC_EXECUTE = 0x2000000;
+
+    private static final int FILE_SHARE_DELETE = 0x00000004;
+    private static final int FILE_SHARE_READ =  0x00000001;
+    private static final int FILE_SHARE_WRITE =  0x00000002;
+
+    private static final int CREATE_ALWAYS = 2;
+    private static final int CREATE_NEW = 1;
+    private static final int OPEN_ALWAYS = 4;
+    private static final int OPEN_EXISTING = 3;
+    private static final int TRUNCATE_EXISTING = 5;
+
+    public static final int FILE_FLAG_BACKUP_SEMANTICS = 0x02000000;
+
     @Override
     public int utimes(String path, long[] atimeval, long[] mtimeval) {
-        UTimBuf64 times = null;
-        if (atimeval != null && mtimeval != null) {
-            times = new UTimBuf64(atimeval[0], mtimeval[0]);
+        WindowsLibC libc = (WindowsLibC) libc();
+
+        byte[] wpath = toWPath(path);
+
+        FileTime aTime = null;
+        if (atimeval != null) {
+            aTime = unixTimeToFileTime(atimeval[0]);
         }
-        return ((WindowsLibC)libc())._utime64(path, times);
+
+        FileTime mTime = null;
+        if (mtimeval != null) {
+            mTime = unixTimeToFileTime(mtimeval[0]);
-    }
+        }
 
+        if (aTime == null || mTime == null) {
+            FileTime nowFile = unixTimeToFileTime(System.currentTimeMillis() / 1000L);
+            if (aTime == null) aTime = nowFile;
+            if (mTime == null) mTime = nowFile;
+        }
+
+        int handle = libc.CreateFileW(
+                wpath,
+                GENERIC_WRITE,
+                FILE_SHARE_READ | FILE_SHARE_WRITE,
+                null,
+                OPEN_EXISTING,
+                FILE_FLAG_BACKUP_SEMANTICS,
+                0
+        );
+
+        if (handle == INVALID_HANDLE_VALUE) {
+            // TODO proper error handling
+            return -1;
+        }
+
+        boolean timeSet = libc.SetFileTime(handle, null, aTime, mTime);
+        libc.CloseHandle(handle);
+
+        return timeSet ? 0 : -1;
+    }
+
+    private FileTime unixTimeToFileTime(long unixTime) {
+        // FILETIME is a 64-bit unsigned integer representing
+        // the number of 100-nanosecond intervals since January 1, 1601
+        // UNIX timestamp is number of seconds since January 1, 1970
+        // 116444736000000000 = 10000000 * 60 * 60 * 24 * 365 * 369 + 89 leap days
+        long ft = (unixTime + 11644473600L) * 10000000L;
+
+        FileTime fileTime = new FileTime();
+        fileTime.dwLowDateTime.set(ft & 0xFFFFFFFFL);
+        fileTime.dwHighDateTime.set((ft >> 32) & 0xFFFFFFFFL);
+        return fileTime;
+    }
+
     @Override
     public int wait(int[] status) {
         handler.unimplementedError("wait");
@@ -343,25 +412,22 @@
     @Override
     public int mkdir(String path, int mode) {
         // TODO: somehow handle the mode
-        try {
-            byte[] widePath = appendWcharNul(path.getBytes("UTF-16LE"));
+        byte[] widePath = toWPath(path);
-            int res = ((WindowsLibC)libc())._wmkdir(widePath);
-            if (res < 0) {
-                int error = errno();
-                handler.error(mapErrorToErrno(error), path);
-            }
-            return res;
+        int res = ((WindowsLibC)libc())._wmkdir(widePath);
+        if (res < 0) {
+            int error = errno();
+            handler.error(mapErrorToErrno(error), path);
+        }
+        return res;
-        } catch (UnsupportedEncodingException e) {
-            // should not really happen
-            handler.error(Errno.EINVAL, path);
-            return -1;
-        }
+    }
-    }
 
     @Override
     public int link(String oldpath, String newpath) {
-        boolean linkCreated =  ((WindowsLibC)libc()).CreateHardLinkA(newpath, oldpath, null);
+        byte[] oldWPath = toWPath(oldpath);
+        byte[] newWPath = toWPath(newpath);
 
+        boolean linkCreated =  ((WindowsLibC)libc()).CreateHardLinkW(newWPath, oldWPath, null);
+
         if (!linkCreated) {
             int error = errno();
             handler.error(mapErrorToErrno(error), oldpath + " or " + newpath);
@@ -379,11 +445,17 @@
         return errno;
     }
 
-    private static byte[] appendWcharNul(byte[] bytes) {
-        byte[] withNul = new byte[bytes.length + 2];
-        System.arraycopy(bytes, 0, withNul, 0, bytes.length);
-        withNul[bytes.length] = 0;
-        withNul[bytes.length + 1] = 0;
-        return withNul;
+    private static byte[] toWPath(String path) {
+        boolean absolute = new File(path).isAbsolute();
+        if (absolute) {
+            path = "\\\\?\\" + path;
-    }
+        }
+
+        return toWString(path);
-}
+    }
+
+    private static byte[] toWString(String string) {
+        string += (char)0;
+        return string.getBytes(UTF16_LE);
+    }
+}