This is a very annoying and confusing error when you first start using SQL 2008. It is caused by SSMS itself, and not SQL.
<p style="text-align: center"><a href="http://egroup.jasonmangone.com/wp-content/uploads/2011/09/SQL_SavingChangesNotPermitted.png"><img class="aligncenter" src="http://egroup.jasonmangone.com/wp-content/uploads/2011/09/SQL_SavingChangesNotPermitted.png" alt="" width="364" height="292" /></a></p>
To make changes to tables through the designer, follow these steps...
<ul>
	<li>Open SQL Management Studio</li>
	<li>Go to Tools &gt; Options</li>
	<li>On the Options window, click on Designers in the left treeview</li>
	<li>Uncheck 'Prevent saving changes that require table re-creation'</li>
	<li>Click OK</li>
</ul>
<div><a href="http://egroup.jasonmangone.com/wp-content/uploads/2011/09/SQL_SSMS_SS1.jpg"><img class="aligncenter size-full wp-image-5036" src="http://egroup.jasonmangone.com/wp-content/uploads/2011/09/SQL_SSMS_SS1.jpg" alt="" width="514" height="297" /></a></div>