Sorry, this is the VirtualTreeViews package which comes with Laz trunk. In case of v2.0 you can open lmlrMain.pas and .lfm, lmlrArchiveForm.pas and .lfm in an external editor, and replace "laz.virtualtrees" by "virtualtrees" in "uses", and TLazVirtualStringTree by TVirtualStringTree; an in lmlr.lpi, replace "laz.virtualtreeview_package" by "virtualtreeview_package". If you have installed the virtualtreeviews package of Laz2.0 then you should be able to open the project now in Lazarus.