Hi; There is a further explanation to this on the actual disney website... but here is some information....
eligible participants can enter without being present in a Disney Property by writing their full name, complete mailing address (including postal code), daytime telephone number (including area code), and date of birth on a 3.5"x5" postcard and sending it with proper postage affixed to: (i) if a legal resident of the United States, District of Columbia, Puerto Rico, Canada or Mexico: P.O. Box 8629, Elmhurst, IL 60126; or (ii) if a legal resident of the United Kingdom: Disney Dream Giveaway, 483 Green Lanes, London N13 4BS. Participants may enter once per day during the Giveaway Period. All mail-in entries must be mailed separately, postmarked by December 31, 2007 and received by January 14, 2008 or they will be void
