Downloaded and attempted to install free version of Spybot S&D v2.3 from www.safer-networking.org/ on system running Win 8.1 Update, but it failed to unpack correctly, giving error code 2, essential files missing.
So I went to http://spybot-search-destroy.en.softonic.com and downloaded version 2.2 which also failed with the same error messages.
Back at first link, I found a link for v1.62 and that installed and runs correctly with Win 8.1U.
Anybody else have this problem or know why..?