non clustered index on same table but the order is different?
It does matter some times. Colleen Morrow does a good demo on this at 
http://colleenmorrow.com/2011/04/07/composite-indexes-does-column-order-matter/

In essence she says that if your WHERE clause contains the first column in the index it will do an index seek. If it contains the third column in the index and not the first it will do an index scan which is not as good. In this case the new index would be better (assuming the optimizer chooses it). If your WHERE clause contains both columns then apparently either index would serve.