How are you copying it?
I had issues the first time I copied it when I used the other tool that's included with the CE rom image... but if you go to the start menu then programs then "Windows Explorer" and use that, it's safer....
Also, there's a tool in there somewhere to show storage space, make sure you have enough.. if you don't delete a map you don't need... (in my case I got rid of Canada and Hawaii )