julian,
here's the tnsnames.ora.........

# TNSNAMES.ORA Network Configuration File: D:\orant\network\admin\tnsnames.ora
# Generated by Oracle configuration tools.

NICK.WAGENBORG.COM =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = laptop_tarry)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = nick)
)
)

EXTPROC_CONNECTION_DATA.WAGENBORG.COM =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC0))
)
(CONNECT_DATA =
(SID = PLSExtProc)
(PRESENTATION = RO)
)
)

WBSH.WAGENBORG.COM =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = nlwgnts7)(PORT = 1521))
)
(CONNECT_DATA =
(SID = wbsh)
)
)

DMV.WAGENBORG.COM =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = nlwgnts7)(PORT = 1521))
)
(CONNECT_DATA =
(SID = dmv)
)
)

WBDZ.WAGENBORG.COM =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = nlwgnts7)(PORT = 1521))
)
(CONNECT_DATA =
(SID = wbdz)
)
)


AS u can see only nick is on my machine.