Help to increase RAM and VGA compatibility

I updated an old PC for my father and now I have 2 problems.

I used an old MSI Master2 Far7 motherboard and 2 Opteron 275 CPU, I bought 2 stick 2 Gbyte DDR400, but the system beeps and didn’t boot. The RAM stick works on ASUS K8N-DL motherboard and even pass Memtest.
I installed a Powercolor HD3850 that worked on my father previous ASUS SK8V motherboard, but now the system doesn’t show anything during boot and windows alert about a graphic card bios error.
I tried also a HIS 4670HD graphic card and in this case the system boot, but without any image during POST.

Is there a way to update RAM compatibility, because the system support 1 Gbyte ECC Registered DDR400 ram chipset and 2 Gbyte ECC Registered DDR333, but fail to boot with 2 Gbyte ECC Registered DDR400?

Is there a way to update Graphic card compatibility?

TIA