Well, that was quite an adventure....
Thanks for the suggestions guys, here's the story.
- disabled nics in bios
- disabled bluetooth in bios
- unplugged usb devices
- Windows 8.1 install crashes while "Getting devices ready"
- confirmed all Windows updates installed
- updated Intel Chipset Driver
- updated Catalyst driver for Asus HD 5450 video card
- updated Asus P8Z77-V Deluxe motherboard BIOS
- Windows 8.1 install crashes while "Getting devices ready"
- updated Intel Management Engine Interface
- updated Realtek Audio Driver
- Windows 8.1 install crashes while "Getting devices ready"
- updated Intel iGPU Graphics Accelerator Driver
- updated Asmedia SATA Controller Driver
- Windows 8.1 install crashes while "Getting devices ready"
- updated DisplayFusion
- updated Hard Disk Sentinel
- updated Classic Shell
- Windows 8.1 install crashes while "Getting devices ready"
- could it be a dodgey background service??
- disabled DisplayFusion
- disabled Hard Disk Sentinel
- disabled Air Video
- disabled FileZilla server
- disabled SoundSwitch
- disabled TED Logging Service
- Windows 8.1 install crashes while "Getting devices ready"
- scanned Asus motherboard forum - no one else is seeing my problem - what is unique about my system???
- set iGPU as primary display and disabled video card in bios
- Windows 8.1 install crashes while "Getting devices ready"
- perhaps my video card hardware is incompatible??
- removed Asus HD 5450 video card
- Windows 8.1 install crashes while "Getting devices ready"
- pretty much out of ideas - decided to inspect my chassis with a flashlight
- mmm... what's that little PCI-E card?
- oh yeah, I installed a Syba 3 port firewire card but never use it and forgot I had it
- removed firewire card
- Windows 8.1 installed successfully!!
Moral of the story: Look for something obvious that few other people have.