If you have given a scammer access to your computer, consider that computer compromised. It is a critical security problem, since they have had access to everything on your computer including all your passwords, so they will all need to be changed. Follow these steps:
1. Disconnect from the Internet
When they have access to your computer over the Internet, they will install a hidden backdoor program that your antivirus won’t find. They will use this to download all the files on your computer and generally mess with your computer.
2. Perform a full backup of your files
You can use File History to do this, you plug in an external hard drive or large memory stick and follow the steps in the File History section of your computer. Alternatively, use Backup and Restore for Windows 7 as it still works for Windows 10.
On a Mac, you can use Time Machine to make a backup of all your files to an external drive.
3. Perform a clean install of the operating system
Run a Windows Reset and choose to keep your files. Windows will move your account and some Windows files to a folder called Windows.old and reinstall a clean copy of Windows to the computer. It will also remove any installed programs you may have installed, so you will need to reinstall any of those programs.
Once Windows is resetting, you can reconnect the Internet. You will need to install all the current patches. Windows will give you a list of them, as well as updating every app in Windows Store.
On a Mac, the process is different, you do this through the Internet recovery mode. Restart the Mac from the Apple menu and choose Restart. Hold down Option Cmd and R to boot into Internet Recovery. You can connect the router at this point and when it connects to the Internet, use the wireless details to set up the Mac, it will start your Mac over the Internet. When you see the Recovery screen, choose to reinstall Mac operating system.
4. Change all your passwords
Giving someone access to your computer effectively gives them access to every account you have, so you are going to have to change every password on every site you have visited.
Important tool: Belarc Advisor
Belarc Advisor is a program that creates a detailed report of your computer, it includes the serial numbers of any program installed on your computer (except Microsoft Office, which you should have printed on the box unless you are using Office 365)