Linking Oracle 10g XE with SQL server using ODBC

Question

I am connecting Oracle 10 XE with an SQL server 2008 using ODBC in windows 7.

I have successfully done following steps:

1. Configured ODBC and test it, runs ok!
2. Configured listener in tnsnames.ora and listener.ora
3. Started listener from command prompt
4. Created database link from interface SQL command line

After creating database link, when i issue a query to SQL server an error is returned: ORA-12154: TNS:could not resolve the connect identifier specified.

Below are the contents of *.ora files:

***************************** listener.ora *****************

LISTENERSQLSERVERDSN =
 (ADDRESS_LIST=
      (ADDRESS=(PROTOCOL=tcp)(HOST=127.0.0.1)(PORT=1521))
      (ADDRESS=(PROTOCOL=ipc)(KEY=PNPKEY)))

SID_LIST_LISTENERSQLSERVERDSN=
  (SID_LIST=
      (SID_DESC=
         (SID_NAME=SQLSERVERDSN)
         (ORACLE_HOME = C:\oraclexe\app\oracle\product\10.2.0\server)
         (PROGRAM=hsodbc)
       )
      )

---

************************tnsnames.ora************

SQLSERVERDSN  =
  (DESCRIPTION=
    (ADDRESS=(PROTOCOL=tcp)(HOST=127.0.0.1)(PORT=1521))
    (CONNECT_DATA=
    (SERVER=DEDICATED)
    (SID_NAME= SQLSERVERDSN))
    (HS=OK)
  )

---

*********************sqlnet.ora***********

SQLNET.AUTHENTICATION_SERVICES = (NTS)
NAMES.DIRECTORY_PATH= (TNSNAMES, EZCONNECT)

---

Please help since i have tried almost every solution found.

thanks,