The first parameter for "bfilename" is a the Oracle directory structure type, not the O/S directory. Change 'C:\WINNT\temp' to be 'ADPHOTO' and it should work.
Couple of things:
1) all functions/procedures accepting the directory structure type is particular about upper and lower case, so make sure 'ADPHOTO' is UPPER case
2) from your CREATE DIRECTORY command, it looked like you were on a unix machine, however for your BFILENAME function, you entered a Windows path. Make sure your file is in the /temp directory of your Oracle server, NOT the client.