Migration Assistant from a Dell

I just purchased a new MacBook Air yesterday and the genius at the store said that I didn't have to migrate everything right from the setup; that I could simply open the migration assistant app and transfer everything after I was done playing around with it. The computer I am migrating from is the Dell Inspiron, and I downloaded the migration assistant onto it as the instructions told me to do. Everything was working great in the migration- all the steps were as the instructions said they should be- until it actually started migrating data. The genius at the store told me that it could take up to 16 hours, so I decided to start it overnight so the next day in the afternoon I could use my Air. When I went to bed it had a "copying Giselle's music" on each screen and the long progress bar was a tiny bit filled, so I was happy because I thought it was working. However, when I woke up this morning the bar was in the same place as it was when I went to bed! It has not moved at all and I'm wondering what went wrong or if anyone else has had this problem and knows how to solve it.

Note: I did everything the instructions told me to do(at the store a genius printed out instructions for me). I plugged both computers in, I kept them at the same pace as I went along with the program, I clicked everything I wanted to transfer, etc.

Thanks!