Index usage question

I have a question on index usage:
I have 2 tables:

CREATE TABLE tblAccountAvailablePlugins (
       nAcctPluginDirID     int4,
       nAvailPluginID       int4,
       sPluginKey           varchar(255),
       nMaxInstances        int4,
       bEnable              int2 DEFAULT 0
);

CREATE UNIQUE INDEX XPKtblAccountAvailablePlugins ON
tblAccountAvailablePlugins
(
       nAvailPluginID
);

CREATE UNIQUE INDEX XAK1tblAccountAvailablePlugins ON
tblAccountAvailablePlugins
(
       nAcctPluginDirID,
       sPluginKey
);

CREATE TABLE tblAccountPluginDir (
       nAcctPluginDirID     int4,
       nAccountID           int4,
       sPluginDirKey        varchar(32)
);

CREATE UNIQUE INDEX XPKtblAccountPluginDir ON tblAccountPluginDir
(
       nAcctPluginDirID
);

CREATE UNIQUE INDEX XAK1tblAccountPluginDir ON tblAccountPluginDir
(
       nAccountID,
       sPluginDirKey
);


When I execute the explain on a simple join query I see that the indices are
NOT used for
the join:

explain select tblAccountAvailablePlugins.nAcctPluginDirID,
tblAccountPluginDir.nAcctPluginDirID FROM tblAccountAvailablePlugins,
tblAccountPluginDir   WHERE
tblAccountPluginDir.nAcctPluginDirID=tblAccountAvailablePlugins.nAcctPluginD
irID;
NOTICE:  QUERY PLAN:

Hash Join  (cost=21.45..640.50 rows=6530 width=8)
  ->  Seq Scan on tblaccountavailableplugins  (cost=0.00..187.52 rows=10452
width=4)
  ->  Hash  (cost=18.76..18.76 rows=1076 width=4)
        ->  Seq Scan on tblaccountplugindir  (cost=0.00..18.76 rows=1076
width=4)

EXPLAIN

can anyone explain me what is wrong with my query?


select version();
                            version
---------------------------------------------------------------
 PostgreSQL 7.1.2 on i686-pc-linux-gnu, compiled by GCC 2.95.3

> Jefim Matskin
> ---------------------------------------------
> Senior SW engeneer
> Sphera Corporation
> Tel: +972.3.613.2424 Ext:104
> mailto:mjefim@sphera.com
> http://www.sphera.com/
>