There are USB to Ethernet adaptors for your computer: these will not work.
You need a network print server (network printer adapter; print server); either wired or wireless.
For wired:
IOGEAR GPSU21 Print Server - $53.00
http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=2000130387&bop=And&Order=RATING
Wireless:
D-Link DPR-1260 Rangebooster G Multifunction Print Server - $64.99
http://www.newegg.com/Product/Product.aspx?Item=N82E16833127074
Others
http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&SubCategory=387&N=2000130387
http://www.tigerdirect.com/applications/Category/category_slc.asp?Nav=|c:16||c:206|
http://www.google.com/products?sourceid=navclient-ff&ie=UTF-8&rls=GGGL,GGGL:2006-45,GGGL:en&q=print+server
Connect a printer or All-in-One to a home network
http://h71036.www7.hp.com/hho/cache/344472-0-0-225-121.html
The best way to network a printer is to connect it directly to your home network by using a network adapter (sometimes called a network interface card, or NIC). This adapter can be either wired -- that is, requiring a cable to hook it until the network -- or wireless. If your printer already has a network adapter installed, it is considered network-ready. If your printer is ready for a wired network, you'll see an RJ-45 jack, (looks like a wide telephone jack), on the back.
Non-network-capable printer: You can still network a printer without a Jetdirect expansion slot using an external Jetdirect box. (Both wired and wireless models are available). The printer's USB or parallel interface connects to this box, which connects to the network. Most external Jetdirect boxes can support multiple printers, including non-HP printers.