Identity Increment = Greyed Out (actually, all properties are greyed out)

I am looking to make the primary key auto increment by 1. I have found by looking around the internet that you need to do this in the Tables -> [Table Name] -> Columns -> [Column Name], Properties window, and I see the "Identity Increment" however all of the properties there are greyed out -- I can't access them.

Any ideas on how to make this work?

For some background:

I'm running SQL Server 2005 with Visual Studio 2005. To create this database, I right-clicked on my project, and went to 'Add SQL Database', I filled in the columns all from within visual studio.

Identity Increment is only avalible for integer types, like tinyint, smallint, int, bigint, etc.