Removing project dependencies

Question

Hello Everyone!!

My question is how to remove project dependencies in Visual studio 2010,
to be specific let us think I am devloping an N-tier application where I have 3 projects A, B and C in one solution. Think A depends on C, B depends on C. By mistake I did the other way, and now when I try to remove the dependencies it shows an error "The dependency was added by the project system and cannot be removed". Any help will be appreciated.

Also I have tried Project Properties > Common Properties > Framework and References section. Still no help and same errors occurs .
 
Thank you
Sandeep.