Oracle Database Express Edition (XE)

Hi, my name is Raul from Spain
I connect with no problem to the Oracle web page and with SQL Line Comands too, but my problem is when I connect to an external tools (SQL Tools 1.5)
I put user=hr, password=hr and TNS value =oradb and the error is ORA-12154.
My TNS_Names files say :
oradb =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = ESRAMIREZR-PC)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = XE)
)
)

EXTPROC_CONNECTION_DATA =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC_FOR_XE))
)
(CONNECT_DATA =
(SID = PLSExtProc)
(PRESENTATION = RO)
)
)

ORACLR_CONNECTION_DATA =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC_FOR_XE))
)
(CONNECT_DATA =
(SID = CLRExtProc)
(PRESENTATION = RO)
)
)

My operting system is Windows 7 ultimate and I only have installed Oracle XE server
Anybody can help me?
Tia.