I checked the box for Modify Registry and ran the app, restarted the machine and still had one of the cards showing a 43 error code.  I then checked the box for Modify Registry and Force, ran the app and also merged the reg file manually then restarted and all cards were working.  I should have restarted first without merging the reg file to test properly but it had been a long day so sorry for the poor testing there.

Headless, I was running windows 7 x64 with 6x Sapphire Tri-x 290's and mining Monero but kept getting lockups with any of Claymore's miners past 3.4 so I decided to give windows 8.1 a try.  I have four of these rigs but testing on two of them, if I remove the monitor and then teamviewer in, all I get is a black screen.  This issue was present before the mod and I have read a few people stating the exact same thing - http://www.reddit.com/r/litecoinmining/comments/1wdawz/headless_windows_81_290x/ - With windows 7 I was restricted to a 640x480 teamviewer window, but at least I could see the desktop and there was just enough space to use the machine, windows 8.1 I get nothing.  I have ordered a few of these - http://www.amazon.co.uk/gp/product/B00C9UB9OK/ref=oh_details_o00_s00_i01?ie=UTF8&psc=1 - as the cards only have dvi-d, hdmi and display port and all of the dvi converters I have are dvi-i > vga.  Fingers crossed.