If there is no application field in the file that matches the pszApp, a new application field is created before the pszKey or pszData entry is made.
If the key name does not exist for the application, a new pszKey or pszData entry is created for that application. If the pszKey already exists in the file, the existing value is overwritten.
Because of the binary nature of the data, the input data is not zero-terminated. Thus, the length provided is the only way to identify the length of the data.
The maximum size of data that can be associated with a key name is 64K bytes. Data in excess of 64K bytes may be written, but there is no mechanism for retrieving all the data.
Deleting Profile Information
To remove the data associated with a given pszKey value for an application, specify a NULL value for pData and a zero length in ulDataLen.
To remove all the data associated with a particular application, use a pszKey value of NULL, a pData value of NULL, and a ulDataLen value of 0.
To remove ALL the data in a user profile, set pszName, pszKey, and pData to NULL, and set ulDataLen to zero.