Definitely nothing to do with my computer.
I've tried 4 different laptops with various configurations. It always resuts in Nokia DLoad with the boot to WP7 following.
The people who have this working don't get the WP7 boot after disk mode which suggests that the bootloader of the phone is acting differently.
So it's entirely down to the bootloader the user has and nothing else as far as I can see.
Although, even with the same bootloader version two users are getting different outcomes so perhaps it also depends on the region of the firmware?
I'm out of ideas
By the way:
Diagnostics App Version: 126.96.36.199
Firmware Revision: ...12070 (I updated just now)
Radio HW Revision: 8255
OEM Device Name: RM-801 SE 615
Device HW Revision: 112.1402.2.3
Note: I have one of the first retail units. It was sent to me by Nokia before the public release.
Nokia 2600 (2004) -> Samsung i780 (2007) -> Nokia 5800 (2008) -> Nokia N8 (2010) -> Nokia C7 (2011) -> Nokia E7 (2011) -> Nokia X7 (2011) -> Nokia E6 (2011) -> Nokia N9 (2011) -> Nokia Lumia 800 (2012)
I still own them all and all still work.