All;
Being technically challenged

, I thought this forum would be a good place to ask some questions that come to mind about attaching an external hard drive to my system so I can play all my tunes and video on my wireless network.
I know this was discussed somewhere, but a search for "NAS" found nothing.
I am unsure as to what I need to buy. Currently I have four computers in the house: 1 wired and three wireless. I am assuming that the external drive would have to plug into the router?
Any help would be appreciated and any suggestions as to actual drives is also good.
Thanks - Mark