Gigabyte GA-7NNXP No Display... Help!

Hi,
Just built a new system and although everything seems to power up ok, there is no display.
I am aware that the AGP slot will only support AGP 4x & above and have tried both a 4x and 8x graphics card without any luck.
I then tried an old voodoo 3 PCI card but still no display. I have tried plugging the 512 mb DDR ram
into different slots and have checked the clock switch is set to auto.
I have also checked the monitor and it works fine on my old machine.
I have now run out of ideas, any help would be greatly appreciated.

I am running
Athlon XP 2800+ Barton
Gigabyte GA-7NNXP
Corsair 512mb DDR Ram 400mhz
450w Antec PSU
SATA 160gb HD
GeForce 2 MX400 64mb

Thanks for any help

\\Toma_Hawk