Nicole Richie & Joel Madden Get Committed 3/9/07

Nicole Richie and rocker boyfriend Joel Madden are getting serious about their romance - they've exchanged rings.

The socialite-turned-reality TV star has taken to wearing her ring on her wedding finger, but friends insist the couple isn't engaged.

A source says, "They are not engaged but they did exchange rings. It wouldn't be surprising if they are engaged in six months."

Richie was recently engaged to Adam 'DJ AM' Goldstein, while Good Charlotte star Madden ended a long romance with pop star Hilary Duff last year (06).