No 'POST' on startup

Hi
I recently put together my first desktop. As it was my first attempt I decided not to buy all new parts. My computer works fine, once booted up, but it doesn't show the POST when switched on. It is quite quick to boot up and works good.
If I connect my monitor to the onboard graphics, the POST shows. I have tried changing 'Quick power on self test' to disabled and enabled, neither make any difference when connected to my graphics card (ATI Sapphire Radeon HD3470).
I just wondered if anyone has had this same problem and has any idea how to solve it!
Gail

What MB do you have?

I am betting in your bios there is a choice for a primary display adapter, which is set to default at the on-board. If you go into the bios with the on-board video check that and change the primary display adapter to PCIe and see if you see post. I am fairly confident you will.

Is this where it says 'Init Display First'??

I tried changing the primary display but this made no difference. I have also emailed Elite Group and they came back with 'buy a newer motherboard, cpu' etc!! Also they say if it works ok when booted, then don't worry!! Basically, it looks like I am stuck with it as it is.
I have another problem now with my other desktop so have re-posted a new thread.

Thank you for your suggestions, all help is very much appreciated.
Gail