If the installation is not completed the first time, ignore the prompt stating that LBA / LBA2 is already installed.
Run the setup.exe which is in the W95 folder on the CD for LBA2 or in the LBA folder on the CD for LBA. It only checks for the presence of the LBA2 / LBA directory. It doesn't check to see if all the files are there. It was assumed that people wouldn't abort the installation.