I'm not surprised you would need a BIOS hack. The HP BIOS is terrible, options are hidden in disparate sections and there is insufficient granularity for booting options.
That's exactly what it does, it allowed me to remove the cd and add 2 extra drives one of which is connected to the esata port. I'm booting from the internal usb and all the drives are seen as individual drives, the 'Onchip SATA Configuration' is set to Enabled and Legacy IDE and SATA IDE Combined Mode to Disabled.
I started using this about 12 months ago replacing a commercial server which was old to say the least.
As soon as I try to load the HDDs, mdadm error.
What's the mdadm error.