I upgraded my avast 2014 internet security suite to the newer 2015 version, and was fine for awhile....until I shut down my computer and restarted it the next day. My brand new computer slowed to a crawl. What normally takes half a second (such as clicking and executing volume control/adjuster) now takes 10 seconds. I made sure it is avast causing the problem by uninstalling, re-installing, and using system restore. Sure enough, when avast is gone from my computer everything returned to normal, and when I re-installed it, my computer turned to mush. This is a major headache. I've been using avast for 4 years, and now it looks like I'll need to turn to another antivirus software.