Problem With Subquery And IN Operator

well here's my problem, i've been working on this homework for about 3 days i got most of my queries work except for the 2 that use nested or subqueries,
i have 2 tables
http://img251.imageshack.us/img251/4623/untitledko5.png
everytime i run the query i get this
http://img251.imageshack.us/img251/7645/untitled2rq0.png
i want the query to show me the costumers that have not made any orders, basically it should show me ID #6 no order,

when i use
SELECT Costumer.ID, Costumer.fname, Costumer.lname
FROM Costumer INNER JOIN [Order] ON Costumer.ID = Order.tblCostumer_ID
WHERE (((Costumer.ID) Not In ([Order].[ID])));

it returns the above pic of a blank query

this is what my POS book says i should type:

SELECT Costumer.ID, Costumer.fname, Costumer.lname
FROM Costumer
WHERE ID NOT IN (SELECT ID FROM Order);

but everytime i try that i get a syntax error after the NOT IN.

i don't know what else to try if anyone could help me out it would be greatly appriciated.