Does it work to use firmware which was originally intended for Windows XP ,run it in compatibilty mode on Vista or 7 and upgrade firmware of peripherals that way ( in this case a Mats**ta UJ 820 D DVD drive ) ??
The operating system should not effect the bios of your optical drive. You should be able to flash the firmware through any operating system. The only issue you might run in to is the software performing the flashing. If that software will not run properly in windows 7 it could not hurt trying to run it in compatibility mode. After you flash your optical drive don't forget to reset the region.