If you have any suspicious about viruses on your computer you need to use an updated Antivirus program to search and remove viruses.
In case of Windows 8 and 8.1, the antivirus application is already installed and ruining in the background. Usually, if viruses are detected you are noticed. In case of older operating systems like Windows 7, Vista or XP, you need to manually install an antivirus software.
Therefore… to scan for viruses you need to:
1. Open Windows Defender application.
2. Make sure you have the latest updates installed.
3. Perform a full computer scan. This might need some time (hours if you store a big number of files on your hard drive).
4. If any viruses found. Perform a clean action.
At this point, Windows Defender will remove or move to quarantine any potential threats or invested files.
Used all information appear large number number of black marks in screen how to remove it guide me please