How would I find out if Office Word is installed on a machine using C#?

I'm currently writing a sample app that installs smart tags to a directory, and I'd really like to know if Microsoft Word is installed, and what version/s are currently installed. Is there a way to do this programatically?

I've thumbed through intellisense and googled but I think my search terms aren't right or something. The closest I've got is the ApplicationID object which seems to refer to the program that I'm writing, not other ones on the machine.

Cheers, Chris