Postgres using 100% CPU

I have a fairly large (about 30Gb) PostgreSQL 8.1 database running on
Windows 2003 Server.
I noticed that CPU utilization on the server is 100% for past few days,
and postgres process is taking up most of that CPU (95%-100%). There is
only one connection to the database at the time and that one is not
doing any queries.

I turned off stats collector, and any row stat collectors, and I
increased the number of check points since I have been getting the
error about check point switches being to frequent. Postgres now uses a
bit less CPU (60-90%), which is still a lot considering that no
processing is being done. Is there anything else I can do to lower this
CPU utilization? Is there a way I can pinpoint exactly what part of
postgres is using this CPU?

Thanks.