Keep on with freedos, USB Stick, HD (or free up some megs and add a Partition). Win is overdose for just running the flasher
if you pull the PCIe Card and just let the USB Stick in ? Otherwise: Dont you have any HD what you can set in the Mac ?
FreeDOS will work fine with a PC card since it uses legacy VBIOS, just like a non-EFI Windows install (where you'll also see a Windows boot logo before the drivers are loaded). You'll just have boot it blindly (e.g. press & hold C).
Burn a DOS 6.22 or other iso image on a CD and try starting it: http://www.allbootdisks.com/download/iso.html
If the CD does not start the DVD drive is the issue. Had once a DVD drive that could not boot anything, changed it with a HL DT drive and no boot problems anymore.
One other thing: Maybe FREEDOS is booting, but you don't see anything because you don't have an EFI card plugged in?
Burn a DOS 6.22 or other iso image on a CD and try starting it: http://www.allbootdisks.com/download/iso.html
If the CD does not start the DVD drive is the issue. Had once a DVD drive that could not boot anything, changed it with a HL DT drive and no boot problems anymore.
One other thing: Maybe FREEDOS is booting, but you don't see anything because you don't have an EFI card plugged in?