Cannot create more than one clustered index on table '%.*s'. Drop the existing clustered index '%.*s' before creating another
This error occurs when a table can have only one clustered index, but it can have many nonclustered indexes. SQL Server uses the clustered index to sort rows so that their physical order is the same as their logical (indexed) order. The bottom (leaf level) of a clustered index contains the actual data pages of the table.
In a nonclustered index, the physical order of the rows is not the same as the indexed order. In a nonclustered index, the bottom (leaf level) contains pointers to rows on data pages, which creates an extra level between the index structure and the data itself.
Use the sp_helpindex system stored procedure to examine the existing indexes on the table. If a clustered index already exists, you must drop it before creating another clustered index.