Walmart believes Amazon’s Achilles’ heel is the costs and delays of shipping online purchases to buyers. Customers who buy some of the more than 1.5 million products on Walmart.com can have them shipped free to a local Walmart, and pick up their purchases at these stores. Internet shoppers may be tempted to pick up other items once they are inside the store. New service desks at the front of some stores make it even easier for shoppers to retrieve their purchases. A Walmart on the outskirts of Chicago is testing a drive-through window, simi- lar to those found at pharmacies and fast-food restaurants, where shoppers can pick up their Internet orders.