When you buy music at Zune Marketplace, you can do it one album or one song at a time (right-click an item and select Buy). You can also use your cart as a staging area for the things you're interested in (right-click and select Add to cart). Right now the cart only holds music, though of course Zune Marketplace also has tons of videos available for immediate purchase.

When you're listening to songs on your Zune—whether songs that people have beamed you, songs that appear in your friends playlists, songs from your CDs, or even songs you're hearing on the radio—track the ones you want to own by adding them to your cart.

If you add a song marked "album only," the entire album the song appears on is added to your cart.

If you want to buy a song from your player using song credits, you must first add the song to your cart.

Your cart holds 50 items (songs or albums), so most of the time you'll see all of your pending purchases. Just make sure you sync first to collect any items that might be arriving from your Zune.

If your cart is full, but you have more music to add from your Zune, those additional songs and albums will be added to your cart as you make room—either by buying or removing a sufficient number of items that are already in the cart. Don't worry, your pending additions will be tracked even if you can't see them yet.