Motherboard wont boot with almost new gpu

[Joshua_178]

I have a gt420, it's only 6 months old. It works in my dell gx280 but it says pcie in x1 mode.......the other motherboard which is a rc415st -hm alhena 5, won't boot at all with the gt420, but the motherboard will boot with another gpu . Which is confusing. The rc415st-hm will beep once when it does boot successfully and it didn't do anything with the gt420, the fans and hard drive spin up and that's all no display,

Specs
Rc415st-hm alhena 5
2gb ram @533mhz
Core 2 duo e4500

 

[helpstar]

if a HP BIOS update won´t help, the gt420 is not compatible to the HP board