رضا: we have more words for the same thing and meaning then we need..

"Have to" and "Must" are the same meaning.. they just show the emotion of the user a bit more..

For instance the young child might say to his friend.. "I have to take out the trash before I can go to the movie"..

and The secretary with a dozen letters to type up and send out, while also staring at a report may say something like "I MUST get this report done before noon so that I can finish the letters" in this case.. the "must" is used to emphasize the importance of what is to be done..

I hope this makes sense!

Kewl board by the way.. Good luck with it!