Insert the OS 3.9 CD into the CD drive and wait until the icon appears on the desktop. Hold down the right mouse button and select "execute command" from the Workbench menu. Into the command field enter newshell and press enter.
A DOS window appears. Enter these commands:
delete sys:c/installer
copy amigaos3.9:os-version3.9/c/Installer sys:utilities
Then close the DOS window and try to install BB1 again.