remove unused meshes Oops schematic ...

ok i open up blender and remove the Cube i go to Oops schematic and se that my Cube mesh still exists i then add Plane and in links and materials setings tab change mesh to Cube now it linked to the removed cube
My question is how to remove objects with meshes so no trace can be found about it …
thinks for any help heres a screen shot


If you save and reopen the Mesh:Cube will be removed if it has no User.