One of the things I have done is create several user accounts.
I have an admin one which allows me to download, remove, install etc and I have created users with very tight controls.
the problem sometimes is that we all log on as ADMIN...with all the rights needed to install items. If we logon as very restricted users its a little bit difficult for items to install them selves as they dont have free access to all the ADMIN systems.
But....I still get some very clever spyware on my system