Ok, I went to connect my N900 to my PC through openssh and when I open WinSCP I enter my user name 'user' and then it asks for password. I have not set a password and tried the default passwords but all are wrong passwords. Also on a different matter, when I enter sudo gainroot and try to execute a program it too asks for a password. I have installed rootsh too. Any ideas what or how to find the password?

There is no passwd for 'user' by default, you have to create one for ssh. For the user 'user' you can do that without rootshasks you for it.

During the install of openssh you were asked to create the passwd for 'root'. One might not be able to decrypt this passwd from the hash stored in /etc/shadow file. You better know it...

I have never had success with 'sudo gainroot'. I always just type 'root' to become root and it does not ask me for a password. YMMV.

I was about to ask the same question about the default user password for SSH. Running 'passwd' as user gave me an error ("The password for user cannot be changed"), but having found this thread pointed me in the right direction. As root, run:
It will prompt you for a new password, not asking for the old one. It said min 5 max 8 characters but I used 4 and it did not complain. The next time I did ssh user@<my N900's ip>, I used the password set as above and... voilá!