Hello Kade,
You can assign/auto-detect computer keys to trigger Hauptwerk's virtual stops and pistons. You can also click on virtual keys to play them.
However, you can't natively use the computer keyboard to play Hauptwerk's virtual keys, but freeware virtual MIDI keyboard applications exist that make your computer keyboard behave as if it were a MIDI keyboard. Such software would send MIDI output which Hauptwerk could receive (thus causing Hauptwerk's virtual keys to respond as if they were played from a real MIDI keyboard), if you configured it appropriately.