Arthur's sister got a call from Microsoft to remove a virus from a computer, which of course was a scam. Now he has to remove it from her computer and is going to format the PC and reinstall.
He's wondering how that scam may have affecter her passwords and data, however. Leo says there's no way to know. There could be a key logger on it that harvests all that information. Since she turned off the computer right away, there's a good chance they weren't able to get anything. If she had waited a few days or weeks to do anything about it, it could have logged all her activity.
To be safe, she should change all passwords and run all updates to Windows after reinstalling to be up to date and secure.