There are two discs:

1.  Buffalo HD-HBU2 ユーティリティCD version 1.20

This will work.  When product number is asked, type in the number on the disc 2

It shows message to upgarde, but no web page exist anymore. But anyhow installed acronis will work in somewhat primitive way.

2. Buffalo HD-WIU2/R1 ユーティリティCD version 3.00

This won’t work.