Writing and Creating a Registry Value
Use the RegSetValueEx function to add a value to or alter a value in a registry key. If the value that you want to change does not exist, RegSetValueEx creates a value and the associated data. You also can choose to name the type of data as you enter the data into the key. Because all of the values are stored and returned in a binary format, labeling data does not affect how Windows CE views it. However, for the sake of a third-party registry editor, you should attempt to label your values appropriately.