I use both the x86 and x64 versions of IE and since Adobe still can't get an x64 version of flash released every time I'm on a site that uses flash I get alerted to install it. It's really anoying now after 2-3 years of using a 64bit browser. Is there a way to stop IE from doing this short of installing the non-existant version of flash?
Short of using a 32bit browser with Flash, or some kind of magic Gresemonkey script that will remove the alerts, there is nothing you can do.
What I suggest is to install a 32 bit browser (Google Chrome is recommended, if not, Firefox) and then install the 32 bit Flash Player. That should work on a 64 bit operating system.