Importing media medium setting image gallery / image attachments

I have recently imported an image gallery to a clean WP install as I am deploying the site to a live domain. I have imported the posts but the images use the medium size for attachements. I would like to get these all to revert to the settings I had set up in the development install.

Does anyone have a idea on how to change the size on already imported image attachements?

Thanks in advance,

J

You can use this plugin: http://wordpress.org/extend/plugins/regenerate-thumbnails/.