You can download Episode I of The Antioch Chronicles here. It requires the full version of Starcraft.

FileSizeContents
antioch1-1.zip5.35 MBWindows self-executing MPQ, readme, missions 1 and 2
antioch1-2.zip5.11missions 3 and 4
antioch1-3.zip4.97missions 5 through 7
antioch1-4.zip5.66missions 8 and 9
antioch1_mac.sit3.53Mac self-executing MPQ

If the self-executing MPQ doesn't work for you, you can kick it old skool and download the voices and portraits separately:

FileSizeContents
antiochports.zip0.98 MBportraits
antiochterrsounds.zip9.71terran sounds
antiochtosssounds.zip7.64protoss sounds

Simply extract these into your Starcraft directory. To turn them off, delete or rename the "sound" and "portrait" directories.

The Antioch Chronicles™ © 1998, Eric Dieter & Ruben Moreno. All rights reserved. The Antioch Chronicles™ trademark and associated logos™ are the exclusive property of Eric Dieter & Ruben Moreno. Characters and distinctive likenesses thereof, character names, item names, place names, named events, artwork and all other related material not disclosed herein are protected under the laws of the United States of America and other countries. Any reproduction, retransmission, or unauthorized use herein is prohibited without express written permission.

StarCraft® is a registered trademark of Blizzard Entertainment. All rights reserved.