Index: boot/bootdata/bootcdregtest/unattend.inf
===================================================================
--- boot/bootdata/bootcdregtest/unattend.inf	(revision 57578)
+++ boot/bootdata/bootcdregtest/unattend.inf	(working copy)
@@ -45,6 +45,10 @@
 DisableVmwInst = yes
 LocaleID = 409
 
+; enable this setting to boot to third stage with a MiniNT boot option
+; (the registry is volatile and no changes are saved to disk)
+MiniNT = yes
+
 ; enable this section to automatically launch programs
 ; after 3rd boot
 ;
Index: dll/win32/syssetup/wizard.c
===================================================================
--- dll/win32/syssetup/wizard.c	(revision 57578)
+++ dll/win32/syssetup/wizard.c	(working copy)
@@ -2039,8 +2039,10 @@
     INFCONTEXT InfContext;
     WCHAR szName[256];
     WCHAR szValue[MAX_PATH];
+    WCHAR szPath[MAX_PATH];
     DWORD LineLength;
     HKEY hKey;
+    BOOL bMiniNTSystem = FALSE;
 
     if (!SetupFindFirstLineW(hUnattendedInf,
                              L"Unattend",
@@ -2142,6 +2144,13 @@
             else
                 SetupData.DisableVmwInst = 0;
         }
+        else if (!wcscmp(szName, L"MiniNT"))
+        {
+            if(!wcscmp(szValue, L"yes"))
+                bMiniNTSystem = TRUE;
+            else
+                bMiniNTSystem = FALSE;
+        }
 
     }
     while (SetupFindNextLine(&InfContext, &InfContext));
@@ -2172,7 +2181,6 @@
                                     sizeof(szValue) / sizeof(WCHAR),
                                     NULL))
             {
-                WCHAR szPath[MAX_PATH];
                 swprintf(szName, L"%d", i);
                 DPRINT("szName %S szValue %S\n", szName, szValue);
 
@@ -2194,6 +2202,32 @@
     }
 
     RegCloseKey(hKey);
+
+    if(bMiniNTSystem)
+    {
+        WCHAR* ptr;
+        DWORD ret;
+
+        ret = GetWindowsDirectoryW(szPath, MAX_PATH);
+        if(!ret) return FALSE;
+
+        ptr = wcschr(szPath, L'\\');
+        if (ptr == NULL) return FALSE;
+
+        *ptr = 0;
+        wcscat(szPath, L"\\freeldr.ini");
+
+        ret = GetPrivateProfileStringW(L"FREELOADER", L"DefaultOS", L"ReactOS", szName, sizeof(szName) / sizeof(WCHAR), szPath);
+        if(ret == 0) return FALSE;
+
+        ret = GetPrivateProfileStringW(szName, L"Options", L"", szValue, sizeof(szValue) / sizeof(WCHAR), szPath);
+        /* in case of error szValue is an emmpty string */
+
+        wcscat(szValue, L" /MININT");
+        ret = WritePrivateProfileString(szName, L"Options", szValue, szPath);
+        if(ret == 0) return FALSE;
+    }
+
     return TRUE;
 }