Ok - I certainly believe that you get 100 errors (or more) when you put the lite-C include files in the VC++ include path. Bill Gates has not yet managed to adapt Visual Studio to lite-C, so the lite-C include files won't go well with VC++.
I explain what to do step by step. With 6 years experience you probably won't need an introduction into the first steps with VC++ 2003

, but here's it anyway:
1. Start VC++ 2003. First you need to create an empty project. Select File / New / Project / Win32 Project. In the field below enter the project name, like "Mandelbrot_Legacy", then click OK. In the following dialog check "Empty Project" under "Application Settings", then click "Finish". VC++ will now create a project for you.
2. Copy mandelbrot_legacy.c into the project folder that VC++ has created, and rename it to .cpp (you're using classes, so it's a C++ program). Add it to the project: In the VC++ Solution explorer, right click on "Source Files", and select Add / Add Existing Item / mandelbrot_legacy.cpp. That should be the only file of the project.
3. Because VC++ does not know about the lite-C includes, you need to edit the path to the litec.h file. Edit the first "#include" line, and give the path to litec.h in double quotes, like this:
#include "C:\program files\litec\include\litec.h"
4. Compile it with Build \ Build Solution, then run it with Debug \ Start.