With an expansion of the Backstreet Boys’ Millennium as one of the few items on their release schedule, Legacy Recordings will go a few steps this further, celebrating the turn of the millennium with a new compilation and a reissue of one of the biggest solo artists of that time. On May 16, Legacy will release an expanded vinyl and digital edition of Britney Spears’ Oops!…I Did It Again for its 25th anniversary. A year before, Spears had ascended to pop’s A-list with her debut …Baby One More Time, becoming the focus of teens (and even…