Finder > Preferences - General. Uncheck "Always open folders in a new window".
Do you mean it opens a new folder when you double click a folder in Finder or when you are browsing through stacks and then select 'Open in finder'?
I mean when I double click in finder it opens new a new window... then when I click another folder, it opens a new window again...
Do you have the sidebar open? Cause if you don't, it will open a new window.
Do you have the sidebar open? Cause if you don't, it will open a new window.
I'm kind of new to Macs, what exactualy do you mean?