Bought one of these a few months back for £20 and have had no problems with it, thought £7 + £4.59 p&p was a fair offer.
P.S. Go easy, never done this before!!
* USB 2.0 Connection for near-universal compatibility
* Fast 150 Mbps Wireless N network connections
* Backward compatible with 802.11b and 802.11g wireless networks
* Secure network connections with a simple push of a button thanks to WPS
* Manufacturer's Lifetime Warranty
Compliant Standard IEEE 802.11b/802.11g (WiFi Certified)
Hardware Interface Type USB 2.0
Humidity Operating: 10 ~ 85%, Storing: 5 ~ 90% non-condensing
Link Rate 150 Mbps (In 40Mhz Mode)
Radio Frequency Band ISM Band: 2400-2483.5 MHz (2.4 GHz)
Radio Frequency Band1 Europe: 1-13
Security WEP (64-128bit), WPA-PSK (TKIP), WPA2-PSK (AES) with WPS Push Button
Supporting Software Windows 2000, XP or Vista