I tryied RDesktop with my XP Box connected via Lan, first i get to a login screen with user and password when i type in my password i get allways wrong password, and now after reboot i get a requester: Error: connect: Connection refused
what am i doing wrong?
Please help

It could be that you are not writing what you are expecting: Remember, the software is simulating your keypresses, there could be something wrong.
Login with the other computer's keyboard, and then open a simple text editor. Then, back on your Pegasos, send some keypresses to the other computer with RDesktop, to see if there's something wrong.

I would:

1) Reboot your PC
2) Verify your account is allowed Remote access by right clicking "My Computer", selecting "Properties", then going to the "Remote" tab, and making sure that the account you are trying to login as has access.

3) Verify your password by typing it in a text editor first to confirm your MorphOS machine is printing the correct characters.

The fact you saw the username and login screen means your connectivity is fine.

In wich editor should i typ it, on MOS side or XP side?

Try to reboot both machines to get a clean setup. Then open a session to your XP box, enter your password in the user's gadget to read if it was transferred correctly. Sometimes different keyboard layouts transfer wrong keycodes. You can check it that way for any mispellings. If it looks correct overwrite it with your username and enter the password below again. Do you still get "Connection refused"?

On the MorphOS side.