first of all you need the wl-hdd version of the twonky installer:
http://www.twonkyforum.com/unsupported/4.4.11/
this package has some sort of install tool for windows that just does everything automaticly.
now go to your router console and see what drivers are mounted
I recalled that twonky installed on /tmp/harddisk
so if it's not mounted on your /opt partition you might want to do so:
now on your windows machine start NASsetup from the twonky package.
just fill in the IP of your router, username and password
and select "install server" and "start server".
click accept and now you should see the beast being installed
when it's done you want to make sure it auto starts every time so we go to post-mount:
now add this line in the bottom of the post-mount.
save it and flash save:
now just point your browser to
http://asusip:9000 and you should see the twonky screen with media browsers and settings (where you can add folders to scan)