You cannot hide these items by changing some portal settings. Instead, you'll have to remove them from your skin. To do so, simply delete the appropriate skin objects from the .ascx file that belongs to your skin.

I suppose that you are using one of the standard DNN skins (DNN-Blue or so). Let's say you use the DNN-Blue - Horizontal Menu - Fixed Width skin. If so, goto the Horizontal Menu - Fixed Width.ascx file in your skin directory, in this case Portals\0\Skins\DNN-Blue\ (if it's your first portal. If not, replace the 0 with the appropriate portal ID). In that .ascx file, look for the HTML table with the skin objects <dnn:CURRENTDATE/>, <dnn:BREADCRUMB/>, <dnn:USER/> and <dnn:LOGIN/>. You can delete these skin objects and replace them with something else if you want, but you can delete the whole table as well.

More details about skinning your portal can be found in the Skinning Guide (part of the DocumentatIon pack on the Downloads page).