Thanks for your suggestions. So the devices are installed correctly and there is a HDMI audio device under the sound devices in device manager. It says it's running/started fine.
I tried booting with legacy on/off. It currently is ON. The system doesn't detect the SSD when in eufi mode and hence can't boot.
Jason, was your previous post saying to simply toggle the legacy boot off, then on again? Or are you saying to turn it off completely?
Also, am I right in saying that if the drive was installed with eufi off, that you won't be able to boot with the eufi on?
Thanks