cmd.exe pops up multiple times

SFC /scannow is only good when there are no viruses on a PC in my opinion otherwise it has greater chance failing to repair windows.

Good malware scanners are malwarebytes and emsisoft are free to use and emsisoft uses licensed bidefender engine and signatures along with its own.

Good free antivirus are avg, avast and avira with avira being superior in my opinion. Also qihoo 360 security which also uses avira and bidefender engine and definitions. However must be enabled after install via settings.

Use both a malware and antivirus scan making sure to enable root kit scan and heuristic checks and alternate data streams check. This will depend on your choice of antivirus and how they set it out.

After updating your antivirus and malware scanner and completed scan and removal any virus then run SFC/scannow

If that fails use windows dism.exe via command prompt which repair windows. Its use is dependent on which version windows you're using eg. Win7, 8 or 10. This you will have to google yourself but I have successful used it on win 7 when SFC failed.