My DH wrote a desktop countdown program for me a few years ago. It's fully customizable; I've changed the pictures/wav file/wording in it for all of our vacations from Disney World trips to Disney cruises to Royal Caribbean cruises.
I hope he still has it on his hard drive because my computer crashed last December and I lost everything.
If I remember to ask him if he still has it I'll come back here and post it.
I have been using DisneyTime (written by Chris Sink in 1997) as my countdown clock. I did a google search and found the following link: http://www.disneyzone.net/countdown.htm
Thanks so much for your responses - I did download the Magical Countdown one of you sent along - many thanks. The one I lost was created by a Chris Foote and had a Mickey icon on it in the shape of an alarm clock. Caroline