On a computer with donet v1 and dotnet v2 installed the flytreeview works. On a computer with only dotnet2 you cannot use the install program. However you can add the dll to the GAC manualy by 'dropping' it into the Windows\assembly folder. The control also needs some client runtime files, which can be copied into the corresponding web folder /aspnet_client/ninerays_web_ui_webcontrols_flytreeview_3_4_3_3/