Only use MSE on XP dual booting with Win 7.
On Win 7 Avast Home is excellent. Version 5 is a good improvement to 4.8.
If ever you try new AV's or firewalls, check search engines for specific removal tools, if they have any then use them. As for Avira then Revo will rid of it.
Worst antivirus I've ever tried. Updating is seriously flawed.