vidalia is a gui for tor. depending on its config, it starts up tor, or a http proxy, or both, or neither.
perhaps you mean "is that what this bundle i installed that i am calling vidalia does?"
torbutton by default points to localhost 8118,
and the polipo that comes with the vidalia by default listens on localhost 8118
s/the vidalia/the vidalia bundle/
same with the tor browser bundle