If that isn't working, there's a good chance your web host has disabled the functionality to set php flags via .htaccess.
I would recommend contacting your hosting provider and tell them you want to disable register_globals and ask them how to do it, or if they could do it for you.
You can most likely change it in a php.ini file specific to your user account, but the location of where that file needs to be and exactly how much of the PHP configuration needs to be included varies depending on how your host has things configured.
So if the .htaccess solution doesn't work, it's probably best just to ask them about it.
