UBB.threads PHP Forum Software Community Forums UBB.classic UBB.classic 5 Support "Board closed" message - What files do this?

I recently switched from UBB to OT. I currently have my UBB closed, and the "board closed" message is directing visitors to the new URL.

I'd like to remove as much of UBB as I can from my server, but I would like to keep the message functioning so that users can find the new board.

What files do I need to leave for this to work? What can I safely remove?

Thanks!