getting on the system

Hi!

I could use some help getting started with Postgresq!. The problem is
that although things worked fine yesterday, now I`m getting permission
denied - could not connect error. System is windows xp.
I wonder if this is related to the setup regarding user accounts, when
I installed pgsql, the program created a new windows system account,
postgres. It is not clear to me what the purpose of this account is,
could someone please elaborate? Also, as I installed pgsql, the
program created a password for the mentioned account that seemed to fit
a security level that I don`t need - how do I change this password? (I
tried setting it upon install but the installer complained it was too
simple).

--
Bruce