How do you download ntsd 2.5 beta

You can't, unless you know the developer well enough or are on his Beta team. Torrent search engines will return bogus results. http://ntsd.open-board.com/forum.htm
There's where you'll get info on this, but be warned..."There is no release date for any version of NTSD or NTSDII. There is no release date for updates on characters. Stop asking. You will be warned for breaking a rule which specifically states not to ask, and be generally disliked by everyone here from the moment you join, including moderators and administrators." (Posted on their board.)