jnjani

YES, I'm referring to this connection (first photograph of white connector). I am connecting this connector at 'ATX 12 V' (located exactly opposite to 24 pin 'ATX POWER' connector) . System will not boot up if I leave it off.

Its a 12 volt square plug usually with two yellow and two black wire and entirely different from ATX 20 or 24 pin plug.

Four pin socket with two yellow and two black wire

Well, this time there IS a change. Removed motherboard from case and started with only 20/24 pin socket. It doesn't shut down - But when I attached 12 volt it again shuts down as previously. There is no beep.

First of all THANKS for superb tutorial. If I could't fix this PC, this tutorial will always be informative and helpful. Now coming to issue, I assume that "internal speaker" refers to Buzzer on board (normally of black colour). If it is true, there is no single beep even. There is no extra hardware. What ever is there is on-board. System is not stable. There is no chance to check anything as it shuts down almost instantly. All I can see is PSU and CPU fan starts for two seconds only. I haven't made any change in hardware of software before this issue. I am sure there is no problem with power supply unit as same power supply works fine in other PC. Just to cross check I have tried other power supply unit with this PC and there is no change.

There is no POST beeps! What next?

Packard Bell Desktop with Intel Dual-Core motherboard shuts down in two seconds. CPU fan and PSU fan starts and shuts down immediately. Checked with spare PSU - No change