Problems with installing Bootcamp

I've had my macbook for over a year now and I decided to try and get Bootcamp on here. Every time i run the bootcamp assist though I get the following error message;
"The disk cannot be partitioned because some files cannot be moved."
What is the best way to fix this or get around it? I really have some windows programs I'd like to use and this is impeding my progress
Thanks for any/all help