Windows

Auto-open at startup

Public Hubs
Opens the Public Hub window at startup, and automatically downloads the configured public hub list.
Favorite Hubs
Opens the Favorite Hubs window at startup.
Favorite Users
Opens the Favorite users window at startup.
Download Queue
Opens the Download Queue window at startup.
Finished Downloads
Opens the Finished Downloads window at startup.
Waiting Users
Opens the Waiting Users window at startup.
Finished Uploads
Opens the Finished Uploads window at startup.
Search Spy
Opens the Search Spy window at startup.
Network Statistics
Opens the Network Statistics window at startup.
Notepad
Opens Notepad at startup.
System Log
Opens the System Log at startup.

Windows options

Open Private Messages in Their Own Window
If you disable this option, a private message from a user appears as a status line in main chat instead of in a separate window. This could cause you to miss some messages if you don't check the chat regularly. You may not care much for private messages from other users. Ignoring them however, not only lessens the (user-friendly) Direct Connect experience, but is not always wise because failing to reply to a message from an Operator can get you kicked or, in the worst case, permanently banned from that hub.
Open Private Messages From Offline Users in Their Own Window
Enable this if you want messages from hub bots in their own window. When disabled they get sent as a status message in main chat instead which is less annoying yet still informative. This option only matters if you're not ignoring private messages from offline users (previous option).
Open New File List Windows in the Background
Keep this disabled if you want newly downloaded file lists to pop up in front of other windows. It can be very annoying to have a new window pop up when you're typing something.
Open New Private Message Windows in the Background
Keep this disabled if you want new private messages file lists to pop up in front of other windows.
Open new window when using /join
When using /join <ip>, a new window with the hub will open.
Ignore Private Messages From Offline Users
Enable this if you wish to ignore private messages from users that are not online on the hub. These messages originate from hub bots and generally contain useful information, like hub specific rules or warnings.
Toggle window when selecting an active tab
With this option enabled, clicking on an active tab will mimic the behavior of Windows 98+ and send the currently active window to the background. The most recently accessed window will become the new active window.

Confirm dialog options

Confirm Application Exit
Enabling this option will cause DC++ to prompt you before exiting.
Confirm favorite hub removal
Enabling this option will cause DC++ to prompt before you remove a favorite hub.
Confirm item removal in download queue
Enabling this option will cause DC++ to prompt before you remove a file (or files) from the download queue.