Two C functions to read from and write to ini-files in C only. (no OS specific API needed!)
Download the source code here: 
Download a sample .ini file:
Usage example:
int main(void)
{
// an example of how to call the functions...
char *value = readFromINI(INI_FILENAME, "Section2", "Entry2");
printf("returned value from readFromINI: %s\n", value);
free(value);
writeToINI(INI_FILENAME, "Section2", "Entry2", "I've changed this value! Weehee!!!");
getchar ();
return 0;
}