Comme quoi Bendes y a pensé, Borland l'a fait !! 
En fouillant dans la doc, j'ai trouvé qu'on pouvait aussi EFFACER en passant un paramètre NULL ! Ze savait pas.. CQFD.
The WriteProfileString function copies a string into the specified section of the WIN.INI file.
This function is provided for compatibility with 16-bit Windows-based applications. Win32-based applications should store initialization information in the registry.
BOOL WriteProfileString(
LPCTSTR lpAppName, // pointer to section name
LPCTSTR lpKeyName, // pointer to key name
LPCTSTR lpString // pointer to string to write
);
Parameters
lpAppName
Points to a null-terminated string that specifies the section to which the string is to be copied. If the section does not exist, it is created. The name of the section is not case-sensitive; the string can be any combination of uppercase and lowercase letters.
lpKeyName
Points to a null-terminated string containing the key to be associated with the string. If the key does not exist in the specified section, it is created. If this parameter is NULL, the entire section, including all entries in the section, is deleted. <<<===
lpString
Points to a null-terminated string to be written to the file. If this parameter is NULL, the key pointed to by the lpKeyName parameter is deleted. <<====
Windows 95: This platform does not support the use of the TAB (\t) character as part of this parameter.
