Monitor error during boot

I have a custom computer: Intel Q8400 Intel DG43G (i know, looking for an upgrade now) radeon hd 5750 6gb ddr2 ram lg 20" monitor Ever since i installed my graphics card, During the boot after the POST beep the screen says "monitor not found, see setup for details, press enter to continue" when i press enter, there is another long beep and the comp starts up fine. however, the monitor in reality is working fine and has no issues. i have the latest drivers for my graphics card. what could the problem be, and how do i fix this? i am moderately proficient with computers, i built mine myself. any help would be greatly appreciated

i'd look in the bios and see if you can turn off the onboard graphics and see if that fixes the startup message.

i'd look in the bios and see if you can turn off the onboard graphics and see if that fixes the startup message.

in the bios/advanced/video config:
the setting was external pcie graphics (PEG)
integrated graphics was not selected (IGD)
i tried setting it to auto and it showed the same error, so its back to PEG now.
im gonna format my pc and see if that fixes it.

to be honest i don't think that'll make any difference. haven't seen such an error myself so no real idea on what the cause may be, whether it's the monitor not sending a signal or something, but i'd be checking connections next. does your card have dual outputs? try connecting to the other one and see if you still get the same error. what type output connections does your card use dvi? if so do you use a vga adaptor?