Well it may be infected file and those that spůsobovat problems
Restart your PC, press F8 to get the black screen to select Safe Mode, and a small guide:
http://www.viry.cz/go.php
Try to eliminate this
http://www.eset.cz/eset-online-skener
http://www.stahuj.centrum.cz/utility_a_ostatni/ant iviry / Single-purpose / Malwarebytes-Anti-malware /

ESET Online scanner to first download to your PC, you will not know if safe mode networks can also download Malwarebytes advance, if possible by computer school for drivers to check and keep away unwanted softwer