From the Musicians Union website
[url="http://www.musiciansunion.org.uk/site/cms/contentviewarticle.asp?article=438"]http://www.musiciansunion.org.uk/site/cms/...asp?article=438[/url]
Works Registration Service – Our new free service for 2007
The Works Registration Service is a free registration, dating and secure storage service intended to assist members in proving when their works were created. We provide a re-writable CD (one per member per year), onto which you can record whatever you want to protect - compositions, recordings, lyrics, artwork, data, etc – in whatever format you want. You then seal the CD in the cover provided and post it to us, post a second copy to yourself by Special Delivery and keep a third copy for reference. If one of your works is infringed then registration with the Works Registration Service can help you prove when your work was created. Proving which work was created first is often a vital factor in successfully prosecuting or defending a copyright infringement claim. For more information contact your Regional Office.