Pardon me if I'm posting in the wrong place about the wrong product, BUT I have an urgent alert for anyone trying to install the avast! 6.0 product vintage March 4, 2011. Specifically, this product cannot be successfully installed in Windows XP Professional (and, I'm sure, "Home" as well) without at least Service Pack 2 (my installation CD has only SP1). If such an installation is attempted, registry issues immediately arise that preclude booting up successfully. However, the "back door" fix for this problem is to boot into Safe Mode, which appears NOT to be affected, to un-install 6.0, and then to re-install an earlier 5.0 or 5.1 version (e.g., 5.1.889). This seemingly obvious problem can take a frustratingly long time to correlate and isolate, but it is very definitely a problem caused by the "premature" installation of avast! 6.0