diff --git a/src/common/filefn.cpp b/src/common/filefn.cpp
index 18cd9ef682..3027b4f575 100644
--- a/src/common/filefn.cpp
+++ b/src/common/filefn.cpp
@@ -1679,15 +1679,6 @@ static bool wxCheckWin32Permission(const wxString& path, DWORD access)
         return false;
     }
 
-    if ( wxGetOsVersion() == wxOS_WINDOWS_9X )
-    {
-        // FAT directories always allow all access, even if they have the
-        // readonly flag set, and FAT files can only be read-only
-        return (dwAttr & FILE_ATTRIBUTE_DIRECTORY) ||
-                    (access != GENERIC_WRITE ||
-                        !(dwAttr & FILE_ATTRIBUTE_READONLY));
-    }
-
     HANDLE h = ::CreateFile
                  (
                     path.t_str(),
diff --git a/src/common/filename.cpp b/src/common/filename.cpp
index 0d6ed2f169..70f131f45b 100644
--- a/src/common/filename.cpp
+++ b/src/common/filename.cpp
@@ -2606,13 +2606,6 @@ bool wxFileName::SetTimes(const wxDateTime *dtAccess,
     int flags;
     if ( IsDir() )
     {
-        if ( wxGetOsVersion() == wxOS_WINDOWS_9X )
-        {
-            wxLogError(_("Setting directory access times is not supported "
-                         "under this OS version"));
-            return false;
-        }
-
         path = GetPath();
         flags = FILE_FLAG_BACKUP_SEMANTICS;
     }
diff --git a/src/msw/pen.cpp b/src/msw/pen.cpp
index a41e4ddf83..843cc88c26 100644
--- a/src/msw/pen.cpp
+++ b/src/msw/pen.cpp
@@ -300,19 +300,6 @@ bool wxPenRefData::Alloc()
    const COLORREF col = m_colour.GetPixel();
 
 #ifdef wxHAVE_EXT_CREATE_PEN
-   // Only NT can display dashed or dotted lines with width > 1
-   static const int os = wxGetOsVersion();
-   if ( os != wxOS_WINDOWS_NT &&
-           (m_style == wxPENSTYLE_DOT ||
-            m_style == wxPENSTYLE_LONG_DASH ||
-            m_style == wxPENSTYLE_SHORT_DASH ||
-            m_style == wxPENSTYLE_DOT_DASH ||
-            m_style == wxPENSTYLE_USER_DASH) &&
-            m_width > 1 )
-   {
-       m_width = 1;
-   }
-
    // check if it's a standard kind of pen which can be created with just
    // CreatePen()
    if ( m_join == wxJOIN_ROUND &&
diff --git a/src/msw/toplevel.cpp b/src/msw/toplevel.cpp
index f275bb5c10..02f28bb566 100644
--- a/src/msw/toplevel.cpp
+++ b/src/msw/toplevel.cpp
@@ -1341,15 +1341,7 @@ bool wxTopLevelWindowMSW::SetTransparent(wxByte alpha)
 
 bool wxTopLevelWindowMSW::CanSetTransparent()
 {
-    // The API is available on win2k and above
-
-    static int os_type = -1;
-    static int ver_major = -1;
-
-    if (os_type == -1)
-        os_type = ::wxGetOsVersion(&ver_major);
-
-    return (os_type == wxOS_WINDOWS_NT && ver_major >= 5);
+    return true;
 }
 
 void wxTopLevelWindowMSW::DoFreeze()
diff --git a/src/msw/utils.cpp b/src/msw/utils.cpp
index 974534be61..93bc29b864 100644
--- a/src/msw/utils.cpp
+++ b/src/msw/utils.cpp
@@ -891,36 +891,33 @@ bool wxShutdown(int WXUNUSED_IN_WINCE(flags))
 #else
     bool bOK = true;
 
-    if ( wxGetOsVersion(NULL, NULL) == wxOS_WINDOWS_NT ) // if is NT or 2K
+    // Get a token for this process.
+    HANDLE hToken;
+    bOK = ::OpenProcessToken(GetCurrentProcess(),
+                                TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY,
+                                &hToken) != 0;
+    if ( bOK )
     {
-        // Get a token for this process.
-        HANDLE hToken;
-        bOK = ::OpenProcessToken(GetCurrentProcess(),
-                                 TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY,
-                                 &hToken) != 0;
+        TOKEN_PRIVILEGES tkp;
+
+        // Get the LUID for the shutdown privilege.
+        bOK = ::LookupPrivilegeValue(NULL, SE_SHUTDOWN_NAME,
+                                        &tkp.Privileges[0].Luid) != 0;
+
         if ( bOK )
         {
-            TOKEN_PRIVILEGES tkp;
+            tkp.PrivilegeCount = 1;  // one privilege to set
+            tkp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
 
-            // Get the LUID for the shutdown privilege.
-            bOK = ::LookupPrivilegeValue(NULL, SE_SHUTDOWN_NAME,
-                                         &tkp.Privileges[0].Luid) != 0;
+            // Get the shutdown privilege for this process.
+            ::AdjustTokenPrivileges(hToken, FALSE, &tkp, 0,
+                                    (PTOKEN_PRIVILEGES)NULL, 0);
 
-            if ( bOK )
-            {
-                tkp.PrivilegeCount = 1;  // one privilege to set
-                tkp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
-
-                // Get the shutdown privilege for this process.
-                ::AdjustTokenPrivileges(hToken, FALSE, &tkp, 0,
-                                        (PTOKEN_PRIVILEGES)NULL, 0);
-
-                // Cannot test the return value of AdjustTokenPrivileges.
-                bOK = ::GetLastError() == ERROR_SUCCESS;
-            }
-
-            ::CloseHandle(hToken);
+            // Cannot test the return value of AdjustTokenPrivileges.
+            bOK = ::GetLastError() == ERROR_SUCCESS;
         }
+
+        ::CloseHandle(hToken);
     }
 
     if ( bOK )
diff --git a/src/msw/utilsexc.cpp b/src/msw/utilsexc.cpp
index a0fbc92115..dedc3f547a 100644
--- a/src/msw/utilsexc.cpp
+++ b/src/msw/utilsexc.cpp
@@ -761,8 +761,7 @@ long wxExecute(const wxString& cmd, int flags, wxProcess *handler,
     DWORD dwFlags = CREATE_SUSPENDED;
 
 #ifndef __WXWINCE__
-    if ( (flags & wxEXEC_MAKE_GROUP_LEADER) &&
-            (wxGetOsVersion() == wxOS_WINDOWS_NT) )
+    if ( (flags & wxEXEC_MAKE_GROUP_LEADER) )
         dwFlags |= CREATE_NEW_PROCESS_GROUP;
 
     dwFlags |= CREATE_DEFAULT_ERROR_MODE ;
diff --git a/src/msw/window.cpp b/src/msw/window.cpp
index a29b0b75bd..4ceb1b076c 100644
--- a/src/msw/window.cpp
+++ b/src/msw/window.cpp
@@ -917,22 +917,9 @@ void wxWindowMSW::WarpPointer(int x, int y)
 
 void wxWindowMSW::MSWUpdateUIState(int action, int state)
 {
-    // WM_CHANGEUISTATE only appeared in Windows 2000 so it can do us no good
-    // to use it on older systems -- and could possibly do some harm
-    static int s_needToUpdate = -1;
-    if ( s_needToUpdate == -1 )
-    {
-        int verMaj, verMin;
-        s_needToUpdate = wxGetOsVersion(&verMaj, &verMin) == wxOS_WINDOWS_NT &&
-                            verMaj >= 5;
-    }
-
-    if ( s_needToUpdate )
-    {
-        // we send WM_CHANGEUISTATE so if nothing needs changing then the system
-        // won't send WM_UPDATEUISTATE
-        ::SendMessage(GetHwnd(), WM_CHANGEUISTATE, MAKEWPARAM(action, state), 0);
-    }
+    // we send WM_CHANGEUISTATE so if nothing needs changing then the system
+    // won't send WM_UPDATEUISTATE
+    ::SendMessage(GetHwnd(), WM_CHANGEUISTATE, MAKEWPARAM(action, state), 0);
 }
 
 // ---------------------------------------------------------------------------