Windows 7 requires that you install the Samsung USB drivers
. It also requires that you have at least Media Player 11 (or later) installed on the computer... which should already be there.
Once you install the Samsung drivers, connect your tablet to your computer, pull down your Notification panel, click on the notification "Connected as a media device" and make sure there's a checkmark in the box for "Media Device (MTP). Windows should then see the tablet and launch a window where you can choose what to do.