installation troubles VirtualBox-4.3.20-96997 on win7 64bit

[batut]

Hi,

First try of VBox installation ended with deep system freeze. After restart I'm unable to go further.
Now I'm getting this uninformative error "Installation failed! Error: Fatal error during installation." when trying to install VBox .

Seems something left from first install is not allowing to start fresh installation.
I can't find a strict instructions of how to totally clear vbox from machine.

Any ideas?
Thanks.