how to restore windows 7 to a know working state every time it boots

A couple of days ago my mother asked me to set up a computer at her house, she wants to use it to basic web browsing, video chat and nothing more.

The problem is, neither my mother nor my sister know anything about using or maintaining a computer.

What I want is to have a working base install of windows 7 and just discard everything installed, downloaded, ... when it reboots. That way I can set up a partition just for saving files and whatever they do the computer will always return to a working state at start up.

can that be done?

PS: Sadly linux is not an option since my sister wants to be able to play some games with my steam account and not all of them run with wine.

You can use Deep Freeze to get that functionality. It restores the system to a prior state on reboot, but leaves folders you specify unmodified. You could also try out Windows SteadyState, a free alternative, but it doesn't list 7 as a supported operating system. Often programs that will work with Vista will work with 7, though, so unless Microsoft have intentionally crippled it I suspect it may work. Otherwise, you might want to consider something like Comodo Time Machine, which can restore your data entirely back to an earlier state.

There's also Returnil - it's "Virtual Mode" does exactly what you're asking for: no changes allowed. After a reboot, the partition is returned to the same state it was in when activated.

There's currently a 1-year giveaway promotion going on now.