PostgreSQL disk space reclaiming

Greetings,

I am having problems reclaiming an excessive amount of disk space used
by a database, running on Windows PostgreSQL v8.3 (unfortunately we are
stuck with this version at the moment).

The database had a 16GB table, that I deleted a lot of data from.  After
deleting from this table, I ran a VACUUM FULL on it and it didn't give
the freed space to the operating system - whats more, running "select
pg_database_size('db')" says that the database is still taking up 25GB.

After this I did some reading, and decided to recreate the table - so I
recreated it with a different name, ran a SELECT * to insert into it,
and recreated the indexes on it.  This new table takes up 3GB only.
After this I dropped the old table, and renamed the new table to the
same name as the old table.  I read on various sites that as soon as you
commit a "DROP TABLE" command, it returns the used disk space to the
operating system.  This did not work either - postgres still reports
25GB being used by the database.  If I select the size of all the tables
in the database postgres reports around 9GB or so, yet reports that the
database itself is 25GB.

After that, I ran a VACUUM FULL across the entire database, and it
returned about 1GB to the operating system, which I think was from
another large table that got cleaned out (but not recreated).

I am now at a loss, as I want the 16GB from that old table back in the
operating system for other means (disk space is severely limited on this
particular machine) and have tried all suggestions I could find from
googling to no avail.  Due to new rules implemented in our data
processing, our database will not grow anywhere near as big as it did
previously - so postgres holding on to all this extra space is a
complete waste also.

Note that it is not really feasible for me to uninstall postgres,
upgrade it and rebuild all my databases at this stage as our system has
a high availability requirement.

Is there anything else I can do to get postgres to give me back all that
unused space?

Thanks for any help people can give!

Anthony Bull

Software Architect
m2Wealth International Ltd.