Too many windows

Why DOpus opens each folder in a new window?
What can i do?
(with W2000 & user account)

Do you mean each folder you double-click within Opus itself (if so, have you edited your Folder filetype's open or dblclk actions or changed it via the registry?) or when you double-click folders outside of Opus, like folders on the Desktop?

i try to change filetype "filetypes/events/dblclk" to "GO" option, but i can't save the result...
how can i edit the registry? (what item?)

You'll probably need to log in as an administrator to edit the filetype actions/events, whether through Opus or through Regedit.