Patch 1.12a

Downloadable Installer Support

If all required Diablo 2 '.MPQ' files are installed on the hard drive, the game will no longer require the CD to play.

For users that originally performed a 'Full Installation'and wish to run without the CD, all '.MPQ' files should be copied from the Diablo 2 CDs to the Diablo 2 directory.
Most users will only need to copy D2Music.mpq from the Diablo 2 Play CD and/or D2xMusic.mpq from the Lord of Destruction CD. Mac users will need to copy these music files and rename them to 'Diablo II Music' and 'Diablo II Expansion Music' respectively.

Anyone who did not perform a 'Full Installation' will need to re-install from CD again to ultimately play without the CD.
In this case, a 'Full Installation' is required, followed by file copy step noted above.

Bug Fixes:

- Fixed an incompatibility between Rosetta and OpenGL mode on Intel Mac.

Download:
Expansion: Here
Normal: Here

From Blizzard for users experiencing difficulties:

Quote Originally Posted by Blizzard
Please reinstall the game using the Full Installation method (with the cinematics) to make sure that all 3rd party files are gone from the Diablo II folder. Once it's done, install the Expansion pack. Once the Expansion pack is installed, go to the Lord of Destruction CD and copy these two files to your Diablo II folder:

d2xvideo.MPQ
d2xmusic.MPQ

Once that's done, run the game and it'll get the patch. You won't need the CD after that.

Some Mac CDs will have the required files in their CD's Support folder. Go there, copy the Diablo II Expansion Music file over to the game folder.