Installer: Add check for supported Windows version

src-installer/RDPWInst.dpr

@@ -1091,6 +1091,13 @@ begin
     Exit;
   end;
 
+  if not CheckWin32Version(6,0) then
+  begin
+    Writeln('[-] Unsupported Windows version:');
+    Writeln('  only >= 6.0 (Vista, Server 2008 and newer) are supported.');
+    Exit;
+  end;
+
   if not SupportedArchitecture then
   begin
     Writeln('[-] Unsupported processor architecture.');