for the past week, i have been getting a lot of pop-ups and too many ads on my browser. i suspected it might be a virus and installed the avast. running the scan, it found 10 viruses and 18 warnings, which i deleted all. i might have deleted some system files so my mac wont start. after the apple logo it shows like an error logo with the processing shaft and it stays like this. pls tell me what i should do now thanks