Solved my issues (no extended display, let alone executing high-performance games on gt540m) by watching lots of videos on youtube... about to flash bios () when (it seems!) the culmination of my efforts finally paid off.

In nvidia CPL, set power to max performance.
In PhysX, set to Geforce.
Personally, I "underclock" to 550,850 -stable settings for me.

also using latest nvidia driver (347.09) which seems to show diff voltage on NVIDIA (previously .98V)

Think my mains adaptor may be degraded, resulting in power supply issues, but I can't prove it (my battery is cr@p, so can't test without mains).

the important thing is it finally works! (for now)