Many things aren't working on my Dell XPS laptop: windows

Many things aren't working on my Dell XPS laptop: windows media player and acrobat reader and wireless connection and trend micro antivirus. Also and the sound doesn't work anymore. I always get this message when I start my computer that C:Windowssystem32AVRT.dll was not designed for windows or contains an error. This problem occurred randomly while I was at school and returned home to these problems.