RegSetValueEx
The RegSetValueEx function sets the data and type of a specified value under a registry key.
LONG RegSetValueEx(
HKEY hKey, // handle to key to set value for
LPCTSTR lpValueName, // name of the value to set
DWORD Reserved, // reserved
DWORD dwType, // flag for value type
CONST BYTE *lpData, // address of value data
DWORD cbData // size of value data
);