BuddyPress.org

Did a quick search and some users experienced a similar issue hosting on Windows – issue with mod_rewrite.

https://buddypress.org/community/groups/how-to-and-troubleshooting/forum/topic/activation-code-after-new-member-registration/
https://buddypress.org/community/groups/welcome-pack/forum/topic/welcome-pack-problem-with-activation-key-s/