Theme Hospital was originally released by Bullfrog in 1997. CorsixTH is an open source clone of the original game with the aim of being able to run on more platforms as well as correcting some bugs and adding new enhancements/features.
CorsixTH requires the resource files from the original Theme Hospital game. If you don't have a copy of the original game you can get the demo version (available here) although it only has one level and is missing several features. Copy the HOSP folder from the original disc to somewhere on your SD/USB drive. When you start CorsixTH for the first time it should show a folder browser for you to locate this folder. It should then restart and go to the main menu.
The original Theme Hospital used midi music, and CorsixTH can play these files. However since the wii has no midi hardware you will need timidity-compatible instrument patch files such as those found at the Freepats project. Once you have a patch set copy the .cfg file you wish to use to "/etc/timidity/timidity.cfg" on your SD/USB drive and put the patch files in "/usr/local/lib/timidity". If possible try and use a smaller patch set which uses substitute instruments, since there's not a lot of memory available (for example if using the freepats set use crude.cfg instead of the default freepats.cfg).
The CorsixTH project is still a work a progress, and there are bugs. Most of the time you'll get an error on-screen asking if you wish to attempt to continue - it's not really a good idea since you'll end up with patients and/or staff stuck in doorways or trying to perform other actions. The best thing to do at that point is to load the autosave file and hope it doesn't happen again.
If you want the true old-school experience, connect a USB mouse and keyboard and play the game just like on a PC (this is actually the only control method that allows you to name savegames anything other than "p").
|Left Mouse Button|
|Right Mouse Button|
|Up (Scroll Screen Up)|
|Right (Scroll Screen Right)|
|Down (Scroll Screen Down)|
|Left (Scroll Screen Left)|
|Pause (keyboard P)|
|Escape (close any topmost dialog)|
CorsixTH uses SDL and LUA, both of which are included in the source archive ready to be built for the wii. Note that SDL has been modified specifically for CorsixTH, I don't recommend using this build as-is for other projects (however some of the modifications are improvements over Tantric's SVN). Modifications to the original CorsixTH source include endian fixes and a LRU cache for the graphics, to make it fit in the wii's limited available memory. It is possible to update the game's LUA files from CorsixTH's SVN as long as no changes are made to the back-end.
The original Corsix-TH project can be found here.