I recently wanted to start playing diablo again and D2 installs fine. When I try to install the expansion it simply says that the classic environment is no longer supported. I'm not very computer savvy but would really like to play some diablo. Any help to how I can install this on my mac would be great.

I would suggest using the digital version as it includes the OSX-compatible installer.

We now offer downloads for many of our Battle.net games. If you have lost your Game CD's and still have your CD-key you can sign up for a Blizzard account, register your game and download the game files. For more information, please visit our Game Download page here:
http://us.blizzard.com/support/article/24813

The game downloaders use the Blizzard downloader to download the necessary game files. For common issues and troubleshooting steps associated with the Blizzard Downloader, please visit our Blizzard Downloader Troubleshooting page here:
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For example some CD-Keys such as older 13 digit Starcraft CD-Keys will automatically update to a new CD-Key once it has been registered online and the new updated CD-Key must be used to install the digital download version of the game.

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