Question: an I install Dragon NaturallySpeaking 10 Legal & Dragon Medical 10 on the same computer?
Answer:

Yes it is possible to install both Dragon NaturallySpeaking 10 Legal & Dragon Medical 10 on the same computer. When completing the dual installation of both versions of Dragon, it is required that you install the Legal version FIRST.
Note:
After installing Dragon NaturallySpeaking v10 Legal, inserting the Dragon Medical 10 DVD should prompt with the following message:
This setup will perform an upgrade of ‘Dragon NaturallySpeaking 10’. Do you want to continue?”
ClickYes” to complete the dual installation of DNS v10 Legal & Medical