Help Getting Top 1 Row For Each Customer

Hi ALl,
I am using SQl server 2005,
I have the following data

customer order_id order_code complete
1328004 3462 18 1
1328004 3463 18 1
1554477 3689 18 1
1554477 4123 18 0

Here I need results like this,

customer order_id order_code complete
1328004 3462 18 1
1554477 3689 18 1

the first row for each customer and order_code, so far I haven't been able to come up with the correct query.

select top 1 a.customer,a.order_id,a.order_code,a.complete
from order a
order by a.customer,a.order_id

My query only returns the top 1 row .Please point me in the right direction.

Thanks in advance