Voice support is just another interface, simple commands will work without any changes, like "open file", "save", "print", "yes", "cancel" and so on.
There is no different for the application if you press a key or say a word, but your speech recognition program must handle these things.
It's like to add a mouse to a command line interface.
It will take a long time, till it will be ready, due recognition of simple words or clear definited sentences is easy, but many many word are so similar to others, that a time consuming training is necessary.
(Did you say "from cd-rom" or "format C" ? ;-)