WinDV is just one option to use w/ the ThumbDV on Windows. You can also use the G4KLX software which works great also. It looks like the Dutch-Star web site is down. I can' t reach it either. Considering the Dayton Hamfest is kicking off, I'd try to have some patience as far as getting a reply from Fred. He's usually very quick to reply. I'd suspect he's probably traveling.
While you're waiting, here's some pointers to getting your ThumbDV working w/ the G4KLX software. First make sure you check out the NW Digital Resource Page:
You'll find a link to this handy PDF file that has several screenshots on how to setup ircDDBGateway & DummyRepeater.
It actually covers setting up the DV3000 & the ThumbDV on Linux & Windows. I highly recommend grabbing the latest versions of both ircDDBGateway & DummyRepeater from the Yahoo Groups. Also grab the AMBEServerWin file from the first URL.
Follow the instructions for using the ThumbDV as a network device. This will save you from having audio issues while TX/RX. There's plenty of web sites out there showing how all this is setup. It might seem a little overwhelming at first, but I promise, it's fun. I've been on D-Star over a year now and enjoyed it a lot. In that time, I've bought the ID-91AD, the 51A+, the 31A, an 880 for mobile use, a 70cm DVAP, and now the ThumbDV and the Star*DV. That's one of the biggest strengths D-Star has over most other digital modes. There's plenty of options out there. :-) I hope the info gets you started. 73 de KB7SQI!