What type of adapter do I need to connect directly to a PC?

The setup:

Linksys g Wireless router, too slow for HD content

HomePlugs connecting router to WD Live, too slow for HD content

Aha!  I just built a Windows Home Server and I can/will hide it in the entertainment center and connect it to the network using the HomePlug.

So the question would be, what kind of adapter do I add to the WHS PC so that the WD Live connects to the PC and not the HomePlug?  My thinking is that all content I watch on the Live is from files.  All content will be stored on the WHS.  If it takes forever to move between my primary desktop and the WHS because I’m using HomePlugs that’s not a big deal.  But I’m assuming that if the Live is connected to the WHS through an Ethernet wired connection then my latency issues will be solved since the movement is between the disks in the WHS and the Live over wired Ethernet.  But what type of adapter needs to go on the WHS so that the Live will connect to the network through it/