XBox Live Membership
With an XBox Live membership, you can download demos or buy and download full versions of XBox games to your XBox gaming system. Although many features of XBox Live require a paid membership, game downloads are not considered a premium feature and are available as part of the basic, free membership option. You can create your account online or through your Internet-enabled XBox.
Internet Access
Because the games are downloaded from the Internet, you will need to establish either a wired or a wireless Internet connection to your XBox 360. All newer models of the XBox 360 come with an internal wireless card that can be used to connect to an existing wireless connection in your home. If you have an original XBox 360, you'll need to purchase an external wireless adapter to connect to a wireless network. If using a wired connection, you need to simply plug one end of a networking cable into your modem and the other end into your XBox.
Compatible Networking Hardware
In order to connect your XBox 360 to the Internet, you'll need to have compatible networking hardware. Generally speaking, routers, gateways and badges marked with "Compatible with Windows 7," "Works with Windows Vista" or "Certified for Windows Vista" will work with your XBox 360. You can check whether your hardware and firmware are compatible by going online to XBox 360 Support and looking for your hardware manufacturer.
Payment Option
In order to download games, you'll need to have a method of payment on record in your XBox Live account. If you have a paid XBox Live membership, you'll already have a payment method on file. But if you have a basic membership, you'll need to attach either a credit card or a PayPal account to your XBox Live account.