You cannot equate strings the same way that you can with variables.

Instead to make 2 strings equal you must use:

str_cpy(STRING* name, characters) //the characters are a set of numbers etc enclosed in the "" marks or the name of another string.

for your code you could write:

function loadLevel(STRING* name)
{
STRING* fullpath;
str_cpy(fullpath, name); //this sets fullpath = to the name string
str_cat(fullpath, "\\config.cfg");
}

//rest of your code here

See if that helps