Your issues are possibly caused by malware that has been installed.
1. If System Restore is enabled and you can go back far enough, restore the computer to an earlier date using Safe Mode. To do so, restart the computer and start tapping the F8 key, select the Safe Mode with Command Prompt option. If you are asked to select
an operating system, use the arrow keys to select the correct one and press Enter. Log on as an administrator or with an account that has administrator credentials. At the command prompt, type %systemroot%\system32\rstrui.exe and then press Enter. Follow the
prompts to restore the computer to an earlier date. You may still need to run your ‘anti’ programs, which you should be doing regularly anyway, to clear up any remnants of the infection.
2. If system restore is not enabled, doesn't go back far enough or doesn’t resolve the issue, boot the computer to Safe Mode, i.e. start tapping F8 when you switch on, then choose Safe Mode with Networking. Now download, save and run a full scan of Microsoft’s
Safety Scanner. Get it here
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