Error in starting Postgresql...

After installing dspace when I tried to connect it to the postgresql
server it gave the following error.

psql -U postgres -h localhost  ( command used )

the error was

psql: could not connect to server: Connection refused (0X0000274D/10061)
          Is the server running on host "localhost" and accepting
TCP/IP connections on port 5432?

I searched for a solution on the net and I found that server might not
be running or postgresql might not have been configured properly.
As far as I know I've configured the postgresql properly..But I'm
unable to find out how to start the pgsql server !!!
Please help me out...