Reassigning middle mouse button

I'm just new into Macs and I am having difficulty figuring out how to reassign the middle mouse button on a two button mouse, so that it DOES NOT activate Dashboard. The Drafting program I am using in Parallels requires the use of this button, but it still activates dashboard when in the program.
HELP!!

Did the mouse come with any software??

Also, you may want to try the program SteerMouse which allows you to reassign mouse buttons...

It's in system preferences>keyboard and mouse on the mouse tab. You should be able to change the behavior of the scroll wheel from there.