hi brother:
may be your system needs some maintain so do the next thing:
1.download and run ccleaner
2.clean junks and registry and uninstall programs that you dont need"one good media player is good",defrag your hard drivers
3.restart your pc
4.ensure that you are not infected :you can download dr.web cure it and run a scan by it to ensure your system is clean.
avast dont hate your pc and it is normal to avast to be big when you open a lot of things,or entering a folder has a lot of programs.
i wish i help you