Not Able To Drop The Index

Here is my code,

1. create table t1 (id int )
2. create unique index u on t1(id)

3. create table t2 (id int constraint f foreign key references t1(id))

4. ALTER TABLE t2 NOCHECK CONSTRAINT ALL
5. ALTER TABLE t1 NOCHECK CONSTRAINT ALL

6. drop index t1.u

I get a FK voilation exception. on line 6.
I was not expecting this, because I am doing 4 & 5

Is dropping the FK is only option?

Actually I am trying to move the unique index to a different file group.




------------------------
I think, therefore I am - Rene Descartes