I recently installed avast on a brand new OS since it is at the top of 2011 polls for most used anti-virus. The problem I am experiencing, is that it slows my system down alot. There is a delay when I first boot up and there is a delay when certain applications are opened. If I am watching a video or listening to actual music, then it will actually freeze that video or music file until the application opens. I never experienced this with my previous install and avira. This is a fresh install, so I am stumped as to why defrag goes from pass 1 to 95% then hangs and why installing avast appears to have broken my windows 7 defragger. I have all 8 shields enabled.