Troubled star Britney Spears has gone back to work to rehearse for her forthcoming single HOT AS ICE. The singer - who's been hitting headlines for all the wrong reasons, including her three-hour stand-off with police at her Los Angeles home and subsequent custody battle no-show - headed to the Millennium Dance Complex in North Hollywood on Sunday (20Jan08) night to practice a new routine for the latest track to be released from her 2007 hit album Blackout. Spears' intense dance session was overseen by studio owner Robert Baker, who tells People.com, "She is working on the choreography for her song Hot as Ice. "She rehearsed an amazing routine with a chair. I let her use my personal copy of Blackout. She forgot her own CD." Baker also revealed that despite Spears' hectic week - which saw her inviting a group of paparazzi into her Beverly Hills, California, home on Saturday (19Jan08) - the 26-year-old was looking particularly cheerful. He adds, "Britney was in an upbeat mood."