Some problem with lend Steam Warband

[Apocalyps]

Hello.
I lend my twice steam(with Warband) for some man some times ago...
He don't know new password to my Steam, but He can run game by Crpg launcher.
So my question is how can I stop it, how can I block them?

[Miwiw]

You can't and you shouldn't have that done.
The thing with warband is simple; it doesn't depend on your steam account in that case as for warband you only need the cd key. The cd key is by steam though ofc, but it is also saved in the registry after installing warband which means he doesn't care about steam at all.