virtualbox.org

Hi everybody!
i have a problem with virtualbox 2.2 and the installation of .net framework 3.5 SP1 (ubuntu 9.04 host, winvista guest).
when i try to install, i get the message "you must use "turn features on or off" in the control panel to install or configure microsoft .net framework 3.5 SP1", but in"turn features on or off" item of the control panel i can't find any item regarding the framework .
Can you help me please ?

TTHHHHHAAAAAAANNNNNNNNNKKKKKKKKSSSSSSSSS!!!!!!!!!!!!!!!

Do you have a native Vista installation? If you do, does that give the same error? Checked google for this problem?

yes, i have a genuine vista but the installation of an application requires the .net fram 3.5 sp1.
i've googled it but nothing.
bye. thank you