Problems Starting Postgres as a Service

Hi

I am trying to run Postgres on Windows as a service and after a bit of
playing around I can run it from within Cygwin and I can install it as a
service OK but when I try to start the service I get the following error:

> IpcMemoryCreate: shmget(key=5432001, size=1499136, 03600) failed: Not
enough core
>
> This error usually means that PostgreSQL's request for a shared
> memory segment exceeded available memory or swap space.
> To reduce the request size (currently 1499136 bytes), reduce
> PostgreSQL's shared_buffers parameter (currently 64) and/or
> its max_connections parameter (currently 32).
>
> The PostgreSQL Administrator's Guide contains more information about
> shared memory configuration.

I have followed all the various how-to's / faq notes etc. and I realise that
the error message has some clues as to a possible solution but could someone
explain why I can start Postgres from the command prompt but not as a
service? Also what are the effects of reducing some of the parameters
mentioned in the error message?

Many thanks

Nick