"Machine check error..." message at the top of the screen when the system boots

What are you putting the image onto, a USB stick or a CD/DVD? I had something similar from a bootable USB with an unpacked iso done by rufus, I had to write it as a "DirectDisk" and effectively nerf the USB stick to be seen as a CD-ROM.

I wonder if it could be the PCIe device, have you tried installing with that unplugged as well (just for testing purposes)

Ruling out the PCIe device is a good guess. Thank you! I come to the same conclusion after I've posted my question. Unfortunately it was not the issue. It turned out to be the BIOS version.

The issue was caused by the BIOS revision. It seems that factory-installed version of the BIOS on the Acer XC-605 had some compatibility issues with Sophos as well as ClearOS. No issues when booting multiple versions of Windows and general Linux distributions though. Once the BIOS was updated to the latest and greatest the issue was gone.

Oh, cool! I wonder if that might be why my Zotac is failing to install. Might have a play while soberingup tomorrow!