I guess somehow it had two installations. Usually Windows Installer uninstalls previous version, leaves the settings and then installs new version (this is all during normal installation).
Since we created new shell extensions (before we had same name for 32bit and 64bit), if this uninstall doesnt go correctly, you could be left with 2… this is not how it should be of course :).
Dual reefers to both 32bit and 64bit, but they are never shown together… 32bit shows only in 32bit programs, such as PA or explorer windows when launched with 32bit programs, because then explorer is 32bit too.