Poonet hi,
First of all you should stick to your other post (http://forum.avast.com/index.php?board=2;action=display;threadid=9276)
Starting another threat for the same thing will not help you more.

The newest version of avast is 4.5.459. Try to get that first.

If you have it but still have problems: Go to Add-remove programs, find avast, press uninstall and when the unistaller pops-up choose repair.

If you want to uninstall avast and clear the registry, first uninstall from Add-Remove, then use this: http://www.avast.com/eng/avast_uninstall_util.html