Yes, sorry if that wasn't clear. I have version 2.0.1.
Do you hear a little sound when you launch the game? For me, D3DOverrider plays a little sound when it takes over on a game. That should indicate whether it's actually working. If you're not getting that sound, maybe play with the "Application Detection Level" setting? Mine is set to Medium, which I think is the default, but I'm not sure.
I also probably have an older version of D3DOverrider, because I got it way back when I originally played the Witcher several years ago. It still works for me though, as I played the bonus Adventures a couple of months ago.
I can't find the version of D3DOverrider, but it came with RivaTuner v2.24.
You might also try adding witcher.exe to the D3DOverrider list manually. I didn't have to, but maybe it will help?
Anyone else know how to get it working?