I have two computers in the house which are linked by an ethernet cables, my wireless router only has one ethernet hole,so I would like to know what I need to buy? such as an adapter or something, so I can have two ethernet cables to connect to my router.the type of router I have is called a Hauwei echolite HG521 broadband wireless ADSL2+ router.Thank you.
If your router only has a single LAN/ethernet port, you can probably patch a switch to that port, then plug your wired computers into the switch. A 10/100mbps switch can be had for as little as $5-10 with some patience. Even an old router w/ integrated switch would work as well. In fact, it might be more economical to simply buy a better router (probably w/ wireless) and use it as a functional replacement for the router portion of your HG521 modem+router.
As a temporary solution, if one of those computers has two network adapters, you could connect its first network adapter to the router, then connect its second network adapter to the other computer’s network adapter, then bridge the network connections on the first computer. IOW, the first computer essentially provides that additional ethernet port you’re seeking.
To bridge the network connections on computer #1, type “ncpa.cpl” (no quotes) at any command prompt and hit enter. When the Network Connections dialog appears, select both network connections, right click to Properties, and select Bridge Connections.
P.S. I don't know how your title "D-link dwl g122 adaptor" fits into all this, you never explained. But of course, if you have a wireless adapter for one of those computers, you don't need a second ethernet port on the HG521 anyway, just use wireless.