Mess USA's Pure Party

12/13/2007 5:27 PM PST
Rehabbed beauty queen Tara Conner celebrated her 22nd birthday Tuesday night like any other girl tryin' to live a clean and sober life -- she headed to Sin City.

We caught the boobalicious pageant princess gettin' her party on at Pure nightclub where she was serenaded by the Las Vegas Pussycat Dolls and presented with a giant, sparking cake. Hello... her birthday's not til December 18!

Also on hand for the big event: Spice Girl Mel B., country stars Big and Rich and butt-whooped boxer Ricky Hatton. Party On!