Thank you. The most useful - in terms of articles - was one of those that Sergey provided. But I will follow your link to the tread as well.

>By strange conincidence here is another thread on this very topic http://social.msdn.microsoft.com/Forums/en-US/transactsql/thread/fca39561-46b5-484b-8674-e7a29dbd8222
>
>>>>Some time ago I set up an alternate key (unique key) index (named AK_CompReference2). Now I want to drop it but when I try to Delete it in the SSMS I get error that "the index cannot be dropped because it is being used in UNIQUE KEY constraint enforcement" But what if I don't want this enforcement any more? How can I drop this index?
>>>
>>>You may want to first drop unique constraint.
>>>
>>>Check http://msdn.microsoft.com/en-us/library/ms177420.aspx
>>
>>I don't see any items/constraints in the Constraints node in the SSMS for this table. The only item I see (that I am attempting to get rid of) is in the Keys node. Here is the script for this key that I want to delete:
>>
>>

>>USE [MyDataBasep]
>>GO
>>ALTER TABLE [dbo].[luCompReference2] ADD  CONSTRAINT [AK_CompReference2] UNIQUE NONCLUSTERED 
>>(
>>	[CompRef2] ASC
>>)WITH (SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, ONLINE = OFF) ON [PRIMARY]
>>