Use Disk Utility to delete your windows partition and re-size your existing partition to use all the space. Just select your drive, go to the 'partition' tab and use the "-" button to delete the Windows partition- be careful, you don't want to delete your OS X partition! Once you've done that, just drag the bottom corner of your OS X partition to fill the whole space and click 'apply'. It'll take a couple of minutes to make the changes, so just be patient and don't try to interrupt the process.
Deleting Boot camp assistant (or any other default system application) isn't the greatest idea - you don't gain much space anyhow.