Me and my friend got WWP working perfectly by doing this:

1. Go to WWP folder find wwp.exe and press properties.
2. Install newest patch. You'll find it here: http://wormsworldparty.team17.com/main.html?page=comm&area=_down_patc
3. Do this... (Sorry picture in finnish, just mark everything on the same places and remember win 2000 compability mode!!!)
http://img255.imageshack.us/img255/8079/wwpmv5.jpg
4. And don't run through Steam!
5. Have fun!

How to get WWP working in Windows Vista:

1. Install WWP.
2. Play WWP.
3. Continue playing WWP, because it works fine.
4. Realise that WWP is vastly inferior to WA since the beta patches started trickling out, and buy that instead.
5. Install and update WA.
6. Play WA.

Honestly, the way people are going on about this problem you'd think that nobody in the world is able to play WWP in Vista.