I have installed a Gigabyte GA-EP43-UD3L, an Intel E6750 Dual Core 2 CPU. GeForce 8600 GT and 3G Memory.
The problem is that when I start the PC the CPU Fan will not work and neither will the fan connected to a System Fan Header. The four lights come on and stay on below the CPU fan header also there is no acknowledging beep.When attached to Monitor -there is no pic or noise. All connections treble checked and seem OK. Checked the memory and no change if any removed.
Has anybody got a clue what is causing this, I have built a few PC's but nothing like this .

Check:

Fans work independent of being connected to the board.
Fans are of the speed control variety and the function and order of the leads match board header pins.
Power supply.

Then:
Do a complete rebuild from square one.

Finally, if problem persists:
Try another board.

Might also give Gigabyte a call. According to the board's documentation, those LEDs indicate CPU loading and the board has some whiz-bang power saving features. Sounds as if board is partially on, if that's possible. *shrug*

A new Motherboard fixed the problem.