title: FileExists is false at network drives when UAC is used?
body: <p>I have found following issue with a CLI tool that accepts files via drag'n'drop.</p>
  
  <p>The file X:\MyApp.exe is a CLI tool which requires UAC elevation (which will be granted).</p>
  
  <p>The operating system is Win7 32-bit.</p>
  
  <p>X: is a network drive to a NAS.</p>
  
  <p>When I drag X:\MyDLL.dll into X:\MyApp.exe , FileExists(ParamStr(1)) will be false. RaiseLastOSError() will show code 3. What am I doing wrong?</p>
  
  <p>It does work when the source file is stored at C: (and dragged into the EXE file).</p>
  
  <pre><code>WriteLn('ParamStr 1 = '+ParamStr(1)); // X:\MyDLL.dll
  if not FileExists(ParamStr(1)) then
  begin
    try
      RaiseLastOSError;
    except
      on E: exception do
      begin
        Writeln(E.message); // (Translated) System error 3. The file could not be found.
      end;
    end;
    exit;
  end;
  </code></pre>