Index: /trunk/src/VBox/Runtime/r3/win/RTSystemShutdown-win.cpp
===================================================================
--- /trunk/src/VBox/Runtime/r3/win/RTSystemShutdown-win.cpp	(revision 39728)
+++ /trunk/src/VBox/Runtime/r3/win/RTSystemShutdown-win.cpp	(revision 39729)
@@ -43,5 +43,5 @@
     AssertPtrReturn(pszLogMsg, VERR_INVALID_POINTER);
     AssertReturn(!(fFlags & ~RTSYSTEM_SHUTDOWN_VALID_MASK), VERR_INVALID_PARAMETER);
-    
+
     PRTUTF16 pwszLogMsg;
     int rc = RTStrToUtf16(pszLogMsg, &pwszLogMsg);
@@ -52,4 +52,8 @@
                                ? TRUE : FALSE;
     BOOL  fForceAppsClosed = fFlags & RTSYSTEM_SHUTDOWN_FORCE ? TRUE : FALSE;
+
+    /*
+     * Do the 
+     */
     if (InitiateSystemShutdownW(NULL /*pwszMachineName = NULL = localhost*/, 
                                 pwszLogMsg,
@@ -57,6 +61,71 @@
                                 fForceAppsClosed,
                                 fRebootAfterShutdown))
-        return (fFlags & RTSYSTEM_SHUTDOWN_ACTION_MASK) == RTSYSTEM_SHUTDOWN_HALT ? VINF_SYS_MAY_POWER_OFF : VINF_SUCCESS;
-    return RTErrConvertFromWin32(GetLastError());
+        rc = (fFlags & RTSYSTEM_SHUTDOWN_ACTION_MASK) == RTSYSTEM_SHUTDOWN_HALT ? VINF_SYS_MAY_POWER_OFF : VINF_SUCCESS;
+    else
+    {
+        /* If we failed because of missing privileges, try get the right to
+           shut down the system and call the api again. */
+        DWORD dwErr = GetLastError();
+        rc = RTErrConvertFromWin32(dwErr);
+        if (dwErr == ERROR_ACCESS_DENIED)
+        {
+            HANDLE hToken = NULL;
+            if (OpenThreadToken(GetCurrentThread(), 
+                                TOKEN_ADJUST_PRIVILEGES,
+                                TRUE /*OpenAsSelf*/,
+                                &hToken))
+                dwErr = NO_ERROR;
+            else
+            {
+                dwErr  = GetLastError();
+                if (dwErr == ERROR_NO_TOKEN)
+                {
+                    if (OpenProcessToken(GetCurrentProcess(), 
+                                         TOKEN_ADJUST_PRIVILEGES,
+                                         &hToken))
+                        dwErr = NO_ERROR;
+                    else
+                        dwErr = GetLastError();
+                }
+            }
+
+            if (dwErr == NO_ERROR)
+            {
+                union 
+                {
+                    TOKEN_PRIVILEGES TokenPriv;
+                    char ab[sizeof(TOKEN_PRIVILEGES) + sizeof(LUID_AND_ATTRIBUTES)];
+                } u;
+                u.TokenPriv.PrivilegeCount = 1;
+                u.TokenPriv.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
+                if (LookupPrivilegeValue(NULL /*localhost*/, SE_SHUTDOWN_NAME, &u.TokenPriv.Privileges[0].Luid))
+                {
+                    if (AdjustTokenPrivileges(hToken,
+                                              FALSE /*DisableAllPrivileges*/,
+                                              &u.TokenPriv,
+                                              RT_OFFSETOF(TOKEN_PRIVILEGES, Privileges[1]),
+                                              NULL,
+                                              NULL) )
+                    {
+                        if (InitiateSystemShutdownW(NULL /*pwszMachineName = NULL = localhost*/, 
+                                                    pwszLogMsg,
+                                                    cSecsTimeout,
+                                                    fForceAppsClosed,
+                                                    fRebootAfterShutdown))
+                            rc = (fFlags & RTSYSTEM_SHUTDOWN_ACTION_MASK) == RTSYSTEM_SHUTDOWN_HALT ? VINF_SYS_MAY_POWER_OFF : VINF_SUCCESS;
+                        else
+                        {
+                            dwErr = GetLastError();
+                            rc = RTErrConvertFromWin32(dwErr);
+                        }
+                    }
+                    CloseHandle(hToken);
+                }
+            }
+        }
+    }
+
+    RTUtf16Free(pwszLogMsg);
+    return rc;
 }
 RT_EXPORT_SYMBOL(RTSystemShutdown);