[SOLVED] Kernel Panic - not syncing VFS: unable to mount root fs

Attempting to install unRAID for the first time. Using the 4.7 stable release. Get the following at boot:

Kernel Panic - not syncing VFS: unable to mount root fs on unknown-block (8,1)
PID:1, commL swapper NOT tainted 2.6.32.9-unraid #8

Ran MemTest, it passes.

Hardware:

Intel D525MW motherboard

2X 2GB Crucial CT25664BC1067.M8FMR DDR3

CoolerMaster GX450 Bronze power supply

Tried several different hard drives. I only have 2 at the moment, need to add a second SATA controller.

Tried each SODIMM by itself, no change.

Tried the latest beta, no change.

Tried the USB stick in another PC, it boots.

This is all new hardware less than 2 months old, and it runs VMWare ESXi with several linux guest distros, so I have to assume the RAM is fine or it would have crashed by now doing that, but it was rock solid.

I don't have any idea where to go next. Any help appreciated.

Found the problem. Have to set USB Boot to 'fixed' in the BIOS.