Open command prompt (cmd) and type "chkdsk" for quick safe mode type of check. If any issues are found it may ask schedule to re-check and repair on reboot. At this point decline the check at reboot but rather type in cmd, "sfc /scannow"...........this will do a more in depth check and repair. Once completed reboot and test, if it works immediately create a restore point.
Its advisable to download either malwarebytes antimalware or emsisoft antimalware as backup scanners but these do find 5-7% of infections otherwise missed by antivirus scanners. Both these apps are free.