Thank you for the tip

After selecting the All Files, it started to show the MPlayer folder, finally.

I've added the line to config and the sync is now better but still one gothca: It's good only for the first one or atmost two minutes, then gradually the video starts to lag behind again.

Also, after the config change, the CPU fan revolves really high (estimatedly as high as 5000rpm) but that's tolerable and not much of a problem. The real problem is to to watch a 720p movie without much sync issues from start to end. Whan more can be done about it?