Can't connet to Oracle from PHP (in IIS)

Can't connect to oracle database.
Error returned from PHP is : ORA_12699.

Code:

putenv("ORACLE_SID=ORCL");
putevn("ORACLE_HOME=f:\orant");

$handle = ora_logon("scott", "tiger");

Evnironment:
Webserver : IIS on Win2000
IIS is on the same machine as Oracle8i server. Oracle8i is install at f:\orant Received on Fri Dec 29 2000 - 22:28:30 CST