how do I get rid of huge sorttemp files?

[root@ds80-237-200-79 6221984]# pwd
/var/lib/pgsql/data/base/6221984
[root@ds80-237-200-79 6221984]# ls -lh --sort=size | head -10
total 9.9G
-rw-------    1 postgres postgres     1.0G Jan  7 12:36
pg_sorttemp10742.0
-rw-------    1 postgres postgres     1.0G Jan  7 12:36
pg_sorttemp10749.0
-rw-------    1 postgres postgres     1.0G Jan  7 12:36
pg_sorttemp10771.0
-rw-------    1 postgres postgres     1.0G Jan  7 12:36
pg_sorttemp10795.0
-rw-------    1 postgres postgres     1.0G Jan  8 17:13
pg_sorttemp3029.0
-rw-------    1 postgres postgres     779M Jan  4 11:39
pg_sorttemp10464.0
-rw-------    1 postgres postgres     599M Jan  7 16:56
pg_sorttemp12913.0
-rw-------    1 postgres postgres     515M Jan  9 17:44
pg_sorttemp2457.0
-rw-------    1 postgres postgres     349M Jan  7 12:36
pg_sorttemp10742.1

template1=# select version();
                           version
-------------------------------------------------------------
 PostgreSQL 7.1.3 on i686-pc-linux-gnu, compiled by GCC 2.96
(1 row)

How do I get rid of these huge files and how do I prevent them from
being created again? The dump of the whole database is ~50 Megabytes
gzipped.

Thanks

--
Markus Bertheau
Cenes Data GmbH