Re: localhost under xampp, windows vista
1) I cannot be 100% sure, as soon as I installed WPMU locally, I continued with the bbP integration, did not stopped to check cookie behaviour.
2 & 3) I am sure I did not go into neither of these two integrations, as I do not know what you are talking about
4) Nope, I never included that define line in my bb-config.php
If you could be clearer about bbPress integration on “bbP side” and “WP side”, I can continue with your suggestions.