Britney Spears has filed for divorce from husband Kevin Federline. Their turbulent marriage allegedly came to an end after a blazing row at Kevin's album launch on Halloween .The 24-year-old singer reportedly screamed at her rapper husband: "You're useless - you're nobody."A source said: "She ran down the stairs crying and stormed out barefoot. Her eyes were swollen and her eyeliner was smudged. She looked like a completemess. Kevin didn't follow her."According to legal documents filed yesterday Britney is citing irreconcilable differences and is seeking custody of their two sons,one-year-old Sean Preston and Jayden James who was born on September 12. Los Angeles Superior Court spokesperson Pat Kelly said: "Yes, it's confirmed. It was filed on Tuesday, on the grounds of irreconcilable differences."The papers state that Britney and Kevin will each pay their own legal fees and the singer has waived her right to spousal support. Britney has also requested that certain belongings including "miscellaneous jewellery and other personal effects" be confirmed as her separate property. It is believed that Kevin signed a prenuptial agreement before marrying the multi-millionaire star. He met Britney when he performed as a backup dancer on her tour. They have been married for two years. Britney and Kevin both spent the weekend in New York, but attended separate events.On Monday night - the date stated by Britney on the divorce papers as the date of separation - she made a surprise appearance on David Letterman's chat show sporting a new blonde bob and trim figure. Britney, 24, apparently surprised Letterman with her arrival and told the host: "I was in town and I just had to stop by. I'm such a big fan."When Letterman thanked her, Britney joked: "No I meant Will Ferrell", who was a guest on the show that night. She then walked off. The 'Toxic' singer has since been spotted partying in New York and was seemingly in high spirits, despite her impending divorce.