A few dedicated Starcraft community members made a mod for Starcraft II that covers the original Starcraft Terran campaign.
Ultraling, Maverck and Jones313 breathed life into Starcraft's original campaign by making it a mod for Starcraft II. Aside from the obvious bonuses to doing this such as having better graphics, higher resolution, as well as compatibility with Windows Aero and 32bit color.
Some of the changes include the addition of medics into the mix, which will change how many have played through the scenarios. Next off they added "snipe" for Kerrigan, along with keeping her original abilities. They also upped the difficulty a bit to keep you busier throughout the whole campaign. There is also mention of a change to Mission 4: The Jacobs Installation, that they do not reveal, but state "you'll see" instead.
They haven't skipped on anything as it seems, with not only the tutorial in there, but they have also included the original soundtrack, voice acting, dialogue and text. They also use custom models with the same structures and statistics as the original.
The mod comes as two separate files. One file is the mod itself, and the second file, is a zip with all the maps. You will need both of them put into proper directories in order to play.
Links
http://sc2mapster.com - The notes and credits.
http://sc2mapster.com - The download page.