http://www.bestbuy.com/site/olspage....=category&cmp=

Just put both items in your cart and check out.

Details:
Get $20 Off Simpsons DVD Offer Conditions

Purchase The Simpsons: Hit and Run for PC along with "The Simpsons: Season 3" DVD and receive $20 off "The Simpsons: Season 3" DVD. Both items must be placed in your cart to receive the offer. If you remove any of the qualifying items from your cart or cancel all or part of your order, you will not receive the promotional offer. All items must ship to a single mailing address. Best Buy's Best Buy's return policy on quantity discounts applies to this promotion.