[discostu]

Windows can be setup to keep user accounts from mucking with the registry and system folders too. Problem for all three OSes is that if you want to install software you're going to have to do it from an account that has administrative priviledges, once you're in that mode they could piggyback spyware. That's how most spyware gets in: while you're installing something else.

[Hunble]

Of course, if you never install software on your computer...

I guarantee, 100%, that you will never have a problem!

[N3WBI3]

But again windows has to be set up that way and when it is it is just as dificult to use as Linux. Also Linux and OSX make sure you know if something is being installed scripting on Windows makes it (in many cases) transparent.