I have this one on my computer and have used it for two years. I had one before that I loved, but a computer crash wiped it out and I cannot for the life of me remember where I found it originally. I like the countdown above because you can add a Disney picture of your choice for the screen saver portion--a nice touch. I used to have the music playing, but turned it off because it was annoying. . . Hopefully, someone else will come along with another option!
You can go to Planning Tools and click on the link that says DisneyTime Vacation Countdown Clock. It should download a zip file with a little disney countdown timer.