The Mobipocket Reader (Desktop) permits you to do direct conversions choosing the import option: click on it, choose the format you want to convert from, choose the folder and file to convert from the window and it converts the file to a prc file.
To create professional looking eBooks you will need the Mobipocket Creator (this is the one that I was “talking” above).
You can get it from Mobipocket site:
http://www.mobipocket.com/en/Downloa...ilsCreator.asp
When installing choose “Publisher Edition” installation, this gives you bigger and better options to format your eBooks.
From the same page where you download the program you have several tutorials who will help you to create your master pieces.
Best,