I am having issues installing windows live messenger in that it claims something is running that is preventing the installation. MS KB article suggests basically doing a limited startup that shuts down all non-MS software (safe mode doesn't work because the windows installer for Live won't run properly in safe mode; I tried). I've got everything shut down but avast won't go. I've been to Settings/troubleshooting and when I uncheck the self-defense checkbox and click ok, it is still checked when I return to settings. I'm not sure Avast is what is causing the issue, but I know antivirus software has the reputation at least of often being interfering software, so I'd like to rule it out if I can. The realtime protection is already off, so it's not that.