Trouble with postgres user's password on Windows

Dear List,

This is my first post, I hope I am asking it on the correct list.

I changed the password for user postgres and I completely forgot about the previous one.

The main problem is that now the postgres server fails to start when I turn on the machine.

It used to start automatically.

To start it, I have to login as postgres and manually start it with postgres -D etc.

Also, on PGAdmin ||| I cannot log in as administrator user , no longer. Even the new password doesn't seem to work...

Can anyone please kindly help me on this issue?

I'd really appreciate it

Thanks a million in advance,
Best,
Oliveiros