I know the last post here is quite a few months ago. But I want to let you know that I've just bought a DM24 with IFFWDM in it. And got it working on win7.
There was a driver-cd with the firewirecard. This driver (v1.01) I've installed on my laptop with win7-ultimate. Then when it asked for the mixer, i've connected the firewire cable, but the computer didn't find the mixer.
After changing the firewire-cable, the computer did find the mixer, and everything is working perfectly now.