The graphic equalizer is not visible in the library mode(the default mode for Windows media player 12 in Windows 7 xx-bit). You must be in the skin mode to access the graphic equalizer or switch to the now playing mode(click on the little squares tab in the lower right corner of the default Windows media player to get to now playing window). The graphic equalizer is selectable from the media player skin you choose or the now playing Windows media player window by right clicking inside the window or from a selectable drop down tab. How the Windows Media Player works in Windows 7 xx-bit is fully described here: Windows Media Player 12
If you want a free graphic equalizer program try the Audacity audio mix/record software suite. For Windows 7 xx-bit use the 1.3.12 beta version.