If you've tried flashing the OS (without -R) then flashing the emmc straight after.. all without unpluging or rebooting the phone and it still isn't working, I'd be tempted to try either

booting Linux (I've got a relatively simple USB stick solution if you have a 2gig stick laying about)

or

using vmware (again, I have a nice little vm that works in vmware player.. you just copy in the 2 bin files and its menu driven (but not pretty)

The errors you're seeing with windows asking you to install support shouldn't matter.. flasher isn;t using a driver in that way.. cancelling any driver requests should be fine..I thought..

a vm or a linux boot might be slightly safer since it rules out any windows problems