I have a Wacom tablet too. I don't recommend it, but yes, you can change it to mouse mode. In the windows menu, search for something like "Wacom tablet properties" (mine is in French). Install the Wacom driver first, if you don't even have it. In Wacom properties, select your pen, and the option is in the "Correspondance" tab to me (which must be the same in English). This is where you choose your screen and tablet sizes. You see a choice:
--Mode:---
*Pen
*Mouse
Choose mouse. Here's a (French) picture in case:
http://imgur.com/ip2gyhgDon't hesitate to ask me if you need anything else.