I have a similar Roland (TS400 I believe) for which I ran a ‘virtual machine’ with xp or 2000 or something running on a more modern operating system (Apples OSX interestingly). So you could run windows 7 on your newer OS (within a virtual machine) and install the firmware that way. I think the virtual machine software I used was either VirtualBox or Parallels but this is going back a little while so I can’t quite remember.