My twinster Jean is, as I write this, on the phone with Microsoft, trying to recover her computer from a bad case of malware. Whatever it is, it deleted the point-in-time copies of the Registry, preventing her from running a system restore.
From this sort of incident, I guess I’d have to say that Vista is the right version of Windows for most people, because it intercepts every attempt to install anything. It’s just too dangerous to be collecting mail and browsing the Web when logged on as an administrator.
My recommendation is that if you’re a typical Windows XP Home user, create a restricted user account and use that for mail and browsing. The only time you should be in as an administrator is if something won’t install in the restricted account and you are sure you want to install it.