Security Issues

I guess this would be an online scam.
My daughter inlaw started getting phone calls from a 'security watch ' type company telling her that her computer had several security issues and she needed to give them her password so they could 'fix' her computer . The first half dozen or so calls she would tell them " no thanks" and hangup.Then the calls kept coming and each one made her more worried ,until one time she actually gave them her password so they could get into her laptop and 'fix'' it for her . Well they sure did 'fix'' it . She has been locked out of her laptop since that phone call .
She ask me what if anything she could do , I have no clue .
I'm guessing they changed her password and changed he user account so even if she were to find some way passed the windows sign in she couldn't change anything.
Has any one eve had this happen if so what did you do to 'fix' it ? Or does anyone have any ideas how to fix this problem ?
I have been very good at not being mean and telling her just how stupid it was for her to give complete strangers over the phone the password. I figure if or when she gets back into her laptop will be a good time to give her s*** about being stupid . Well ,I did mention that I could have been a great help if she had called me before giving out her password .

First of all, make sure to disconnect the computer from internet (or network if you're on a public network), so they can no longer access the computer.

The next steps depends on your operating system, your experience with computers, and whether you have important data on the computer.

The simplest and most secure solution is to reinstall the operating system and making sure to format, or at least delete all files on system partition. But if you have important data you will have to make sure they are not on system partition, or if they're, you need to back up them first.

There are other solutions and workarounds, but they depend on your situation details.

Thank you for replying.
She finally just took it to the place she bought it and the tech was able to get into windows .
It is a lap top and the guys on the phone she gave her password to changed her pass so she couldn't get past the sing in page.
She had all their banking , bill paying , budget ,, every thing on it . When she figured out what had happened she was quick to call the bank and their cards letting them know . So it could have been lot worse then her being inconvenienced and embarrassed .
I Never have done my business online . I keep a pre pay debt card from Walmart loaded with a few dollars and that is what I use to pay my ISP and anything else that I order online . Plus I don't ever give some nut on the phone my pass word