Hi thete,
To which chapter / page number of the book are you referring? If this is not about my book, you're better off posting this in a more general ASP.NET category here:
http://p2p.wrox.com/asp-net-4-539/
That said, deleting requires a primary key in the database tables, so make sure the table has one before you drag it on the design surface.
Cheers,
Imar