I have the original install disc but my OS is to new to allow installation (10.6). What is the OS that will allow me to install it?
Link the key to your Bnet account and DL the installers from there.
10.6? As in Snow Leopard? Or is that a typo and you are on 10.16? If you are on 10.15, 10.16, or 11.0 (Big Sur), the original Diablo 2 installers will not work even if downloaded from Battle.net using your linked keys because they are 32-bit apps and the OS no longer supports 32-bit apps.