Oracle Database Discussions

My Database
Oracle XE 11GR2 (Windows x64)

Connecting to
SQL Server 2008 R2

OS: Windows 7 (both database are in same machine)

I have followed the instructions here: http://www.databasejournal.com/features/oracle/article.php/10893_3442661_2/Making-a-Connection-from-Oracle-to-SQL-Server.htm

I can TNS ping my new link in tnsnames.ora however when I run queries against the database link I get this error:

+SQL Error: ORA-28545: error diagnosed by Net8 when connecting to an agent
Unable to retrieve text of NETWORK/NCR message 65535
ORA-02063: preceding 2 lines from MYSQLSERVERDSN
28545. 0000 - "error diagnosed by Net8 when connecting to an agent"
*Cause: An attempt to call an external procedure or to issue SQL
to a non-Oracle system on a Heterogeneous Services database link
failed at connection initialization. The error diagnosed
by Net8 NCR software is reported separately.
*Action: Refer to the Net8 NCRO error message. If this isn't clear,
check connection administrative setup in tnsnames.ora
and listener.ora for the service associated with the
Heterogeneous Services database link being used, or with
'extproc_connection_data' for an external procedure call.
DESC d0.resc@mysqlserverdsn
ERROR:+


Given the article is dated 2004, it probably wasn't a good idea following it as those concept may not work with 11G database. Then I came across Oracle Database Gateway, but have no idea how where to download the OUI which sets it up.

Would anyone know any good articles or links which highlights step by step how to accomplish setting up a DB link between SQL Server and Oracle Database? Cheers.