Password Authentication Error

Hi

I have just installed PostgreSQL 8.1 on a Windows XP system with a
NTFS filesystem. Everything seemed to work fine until I executed the
command promt option from the PostgreSQL start button.

I wanted to create my first database by typing "createdb mydb" and
was asked for my password. Everytime I type it in I get the error message
"createdb: could not connect to database postgres: FATAL: password
authentication failed for user "xxxxx" ".

Another problem is that the user xxxxx in the error message is not the
user specified in the installation (I used the default user "postgres"
given in the installation) but my username on my computer and it has
administrative rights.

I dont really know why PostgreSQL asks for my username and not the one specified
in the installation.

If anybody can tell me why I get this error everytime I would greatly
appreciate it.

Johan van der Merwe