I had some problems with my 1.2.4 installation, so I ended up downloading 1.2.6 and removing all raes of my earlier installation.
When I try to install virtualtreeview_package 4.8.7.2 nohing happens except in "Messages" it states
"make: Leaving directory `D:/DevTools/lazarus126_fpc264_win32'"
This happens when both using "File | Open..." selecting packing, compile and then "Use >> Install" or in the "Package install / uinstall packages" dialog...
If I after trying to install restart Lazarus and go to "Package install / uinstall packages"
virtualtreeview_package 4.8.7.2 is listed to the left under "installed", but... if I look into "Package info" it says the following:
Author: Mike Lischke (LCL Port: Luiz Américo)
Description / Abstract: Virtual Treeview is an advanced component originally created for Delphi
Filename: D:\installed components\VirualTreeView_lazarus\virtualtreeview_package.lpk
Current state: selected for installation, not installed, RunAndDesignTime
So apparently not installed afterall which also explains why I do not see he components on the the componen palette.
For referance, I have installed lclextensions.
Note. I have created a new post here with command line log - since I believe it problem is not specific to virtual treeview:
http://forum.lazarus.freepascal.org/index.php?topic=27102