Supposedly the BlueStacks emulator allows one to run the Rift Android mobile authenticator on a PC. The first URL has a link to the download, and the second (dated last January 2012) talks about BlueStacks.
http://www.mmo-champion.com/threads/1151408-Rift-Mobile-App-without-android-apple-smartphone
http://samsunggalaxyandroid.net/2012/01/bluestacks-app-player-out-of-alpha-beta-bound-soon/
Apparently BlueStacks is still in beta.
http://androidcommunity.com/bluestacks-app-player-for-windows-enters-beta-20120327/
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