Paris Hilton partied at a Hollywood club on Saturday -- the first time the she has enjoyed herself at a nightspot since her release from jail last month.Hilton, who served 23 days of a 45-day sentence after being found guilty of violating her probation from a 2006 drunk-driving arrest, was accompanied by her sister Nicky at Los Angeles club Les Deux.One onlooker tells People.com, "Paris was super happy and full of smiles. She was laughing, having fun, drinking, dancing, singing along to songs, talking to everyone and hugging all the girls at her table."After her release from jail, Hilton vowed to put her wild partying days behind her.She said, "I've been doing it for a long time. It's fun. ... But that's not what I care about as much anymore. Obviously I'll still go out sometimes. I'm young and I like to be social, but I'm going to focus more on my work."