shared_buffers, work_mem and mantenance_work_mem in Windows

Hi,

I have not been able to use the tuning wizard in windows for postgresql
8.4 since it stops postgres starting so I have been looking to tweak the
postgresql.conf file directly. I am happy with the performance of
postgres in general but I feel that it is not utilising the memory on my
servers to its full potential so I am looking for some tweaks to get it
turbo-charged.

There seems to be little documentation on tuning these settings for a
Windows based machine and many of the performance tuning notes I have
found seem not to apply for version 8.4. One example of this is the
maintenance_work_mem which now runs out of memory if I set it to values
that I used for previous postgres builds (512MB).

I have lots of unutilised RAM on my system, and so I try and increase
the shared_buffers on my server to 2GB, however postgres will not start
when the value is set this high, so at the moment it is set to 512MB.
Are there any optimal settings for this on windows.

The third value I am experimenting with is work_mem, which at present is
set to 12MB - but memory still appears to be unused. I have a test
system with 3.5GB which rarely appears to go over 1GB and a production
server with 8GB which barely touches the RAM.

I would really appreciate anyone pointing me in the right direction with
regards tuning an 8.4 based windows machine.

Thanks.